That terrain resistance is exactly the same as the IS-7, I think, and it has roughly similar HP/ton. The IS-7 is not exactly super slow, anyway.
I honestly think the speed is fairly reasonable. You need to consider the fact that the gun is very, very good on the Object 277. In fact, it might be one of the best guns of all HTs in the game, because it has literally everything. SConq doesn't have alpha nor overmatch potential. Not only the 277 has 490 alpha, overmatch capability and fairly good DPM, it also has good aim time, very nice base accuracy, quite solid shell velocity, good dispersion values and the best penetration of all HTs in the game. 265 AP is really nice and comfy, and 350 HEAT is very strong in current meta, especially on a reliable, hard hitting gun. The gun is so much better than IS-7's that it's not even funny. 5A's gun is also quite potato compared to 277's.
We don't know the actual armor layout, but it seems to be much better than on the T-10, and probably better than on the 5A. It's not a real pike nose either; it's more like the egg shape hull of the US tanks. Due to that, it should be able to sidescrape better than the T-10 and 5A, and probably not be much worse on that than the IS-7. Hell, the turret seems very good as well (again, likely better than 5A's, unless the cupola is really, really weak and bigger than it seems, or if it has overmatch spots). And there is a chance that the entire side armor is 114 mm thick; in that case, the lower side armor would be better than IS-7's. The armor is probably not THAT much worse than on the IS-7.
What I predict is that the 5A and IS-7 will both be better tanks for CW than this. 5A has -7 depression and DPM, IS-7 has HP and near-gold-immune turret (I feel like the turret of 277 will still be pennable on some areas, at least on cupolas). However, 277 has super comfy gun, and the armor and mobility seems good enough. It probably bullies lower tiers very well, and due to comfiness of the gun, is probably more fun to play than the IS-7 and 5A. So, with that in the mind, the 277 is probably a more fun pub tank than neither IS-7 or 5A. In fact, it should be a very nice tank for pubs, just because the gun stats alone.
Will wait and see, though. Personally I would probably make the armor shittier but mobility better (by buffing resists), but I'm gonna wait until this tank hits test server.
K-91 seems trash, though