Fuso - lacks in tankiness but compensates with best firepower in tier. Weak to airstrikes and torps because of poor handling, mediocre torpedobelt and non-existent AA. Good bote but I wouldn't rank it as god tier.
Mutsu - flexible, low armor, massive guns that overmatch everything in sight (shit raw penetration though), and once again no AA to speak of and poor handling, but you're the 2nd fastest T6 BB. On the other hand, you have 4x1, 2 per side torpedo launchers with very narrow arcs, you're gonna use them once in a blue moon but hey, they're torps on a BB!
NM - Slow, tough as nails, many guns with very good pen but wonky accuracy, AA is pretty hefty but still nowhere near Cleveland-levels of no-flight-zone
Arizona - more accurate guns with lower pen, a bit tankier than NM, still slow as a Maus in Lakeville valley, AA is almost nothing to speak of. If there's not going to be many CVs, I think AZ is straight up better than NM and is definetely a top pick.
Bayern - incredibly tough, much of the ship is covered in non-overmatchable armor (which also means HE can't pen you there either), gunners tend to drink too much bier guns do overmatch but they have shitty raw pen and questionable DPM. You're reasonably fast and very maneuverable. For me, the Bayern is a godsend, some people seem to hate it mainly because of guns, bout you're so tough you can get up close and personal and just demolish every other BB save for, maybe, Warspite.
Warspite - very similar to Bayern in most regards, except it trades some takiness for absolutely incredible guns, with excellent accuracy, penetration and the ability to overmatch. Cruiser DCP means you can get more liberal with blowing it on fires, and a Repair party that heals 33% of citadel damage instead of the usual 10%. AA, what is even AA? You're however, extremely maneuverable so any potential airstrikes can be evaded with ease. Top tier pick as well.
Dunkek - very fast, flexible, best raw penetration in tier and fastest reload time. However, this is where the good stuff ends. Weak armor all around means you'll get overmatched and penetrated by HE all the time, guns have shit DPM, AA is non-existent and the ship is so looooong. You could probably get away with much kiting and repositioning, but if you sit bow-on, she melts very fast.
Aoba is a weird one. You have shitty DPM but your guns are still 203mm, which means you have very high fire starting potential, excellent AP, you can HE pen more areas on BBs than you would with other cruisers. But you're not gonna be much of a threat to DDs or planes. DFAA saves it from getting annihilated by CVs. Not bad but not god-tier either.
Cleveland - short of god-tier. Unmatched firepower, AA and HP with shit concealment, armor (you melt under HE and you're so big that BB AP is going to hurt really bad) and very floaty shell arcs.
Budyonny takes my prize for the top cruiser pick. Very comfortable range, excellent guns in every aspect, pretty tanky for a cruiser and workable AA. Only bad things are the yuuuuge turning circle and a long citadel
Molotov - bussian rias 180mm doomcannons and that's pretty much it. It's a very long sausage just waiting to get dev-striked by BBs and CVs. If you can evade focus it's a very good ship, but it gets deleted so easily.
Memeberg - with the upcoming 360noscope turrets and free IFHE it's moving up from shit-tier to mediocre tier. It gets deleted even more easily than Yolotov and guns, while having great DPM, have such wonky ballistics that I struggle to hit anything further away than 10km. You have a scary torpedo suite though, if you can ambush somebody around a corner you'll probably win the fight (but such scenarios happen once in a blue moon). With the maps you'll get in T6 ranked the long range German Hydro might prove quite useful
Graf Spee - the tankiest T6 cruiser with very scary guns (that, mind you, have very wonky accuracy) and a set of long range torps. You also get 40k HP, Repair party and the choice of DFAA and German Hydro. Personally I'd rank it very high
Leander - a very good oversized DD. It can fire exclusively AP with special characteristics (short fuze which means you almost never overpen and very good bounce angles), has a solid torpedo suite and gets acces to Hydro, Smoke (deploys for only 7 seconds and lasts very long, so you have to slow down to ~19kts before you start blowing it, the cloud is very large so teammates can hide in it too) and Repair Party. No armor to speak of which is sometimes a good thing, as you're very hard to citadel from close range. A very good pick that requires much skill to pull off.
Perth - Leander's sister ship, but it has normal AP as well as HE, loses the access to Repair party but gains a catapult aircraft, and the main difference is her smoke screen. It deploys for 100 seconds but each individual smoke cloud lasts for 10 seconds. What this means is that you can be cloaked while moving around at 12.5kts for more than a minute and a half. If you can get near a cap undetected, pop your smoke generator and hydro and take the cap essentially for free. Once your smoke runs out you're gonna have to hide around for nearly 3 minutes. It's a very niche ship that hasn't got much use outside of securing caps, there are muany better ships for dealing damage.
Duca d'Aosta - she's a contradictory boat. Has access to both DFAA and Hydro as well as a catapult plane. Short gun range of only 14km, but her shells travel extremely fast. AP has low pen and HE has low fire chance, which means low DPM, but her torps are pretty special - very slow at 51kts with 12km range. She is extremely fast so you can close into cap zones faster than some DDs and get out quickly once the enemy BBs start showing up. A very solid cruiser in general even though it's kinda weird.
Fubuki - why take it when the Shinonome exists?
Shinonome - a straight up better Fubuki. 3 triple torpedo launchers that deal 2k less damage, travel 2km less and are 4kts faster compared to Fubuki torps. She can actually defend herself since she has 50% more gunpower, and you're definetely going to want to be aggressive and contest caps in ranked. A very good pick, especially for clearing out smokes which I reckon are going to be even more prevalent now that there's no Radar at T6
Hatsuharu - the worst T6 DD by far. Shitty guns, only 2 triple torp launchers. Only thing going for her is best-in-tier stealth.
Farragut - top tier pick. Brings excellent utility in form of long-lasting US smoke and has unrivaled gunpower in tier which means she is an excellent cap contester and gunboat in general. Her torps only have 6.4km range so you won't be stealth torping anything. Also, don't bother with the C hull, you trade 1 gun for DFAA which is not worth it, even in ranked.
Gnevny - a slightly worse Anshan with slightly better fire chance. Great if you're not the only DD on the team because you simply can't stealth torp
Anshan - a better Gnevny and a very good pick. Powerful long range guns with shit turret traverse that makes her bad in close encounters, 8km torps (compared to Gnevny's 4km) that enable her to stealth torp, high speed and utility in form of smoke.
Ernst Gaede - very good at cap contesting. Beefiest HP pool of any T6 DD, Hydro on a DD, very punchy 150mm guns and fast 8km torps make her a great all-around DD. Only real downsides are shitty DPM and very short lasting smoke.
I can't tell you much about CVs except that Independence is very flexible with her loadouts and her fighters are straight upo better than Ryujo's, while Ryujo has better strike potential while not sacrificing fighters (unlike Indy's 0-1-2 loadout) but requires better micromanagement due to more squadrons.