The camera can judder at times (most noticeable on horse when trotting) so perhaps it's that which is making it look less smooth than it should be. The 1.05 patch was supposed to fix that I think but I didn't notice any improvement.
I'm not sure if there is an actual limit on how much you can carry. You just become overburdened when you go over your weight limit, but you can still loot, fight and jump up ledges so it's not restricting. The only things you can't do is run or roll after landing I think.
Vinny took ages killing the wraith but it went down quickly when he started using Yrden on it, which helps immensely in fights against them. Could be that the time clicked over to night around the same point though. I'll have to watch it again and see if that is the case.
Coin isn't a problem later in the game, or at least it hasn't been for me. I have around 12,000 crowns at the moment. Though I've been looting/selling much more than spending throughout the game.