Since horses max out at level 50, and they gain a level each time you feed them to increase their stats, is there a way to change them after? If I want to change the attributes from a lot of carrying capacity to speed instead it would be nice to know if that's possible. Or is it better to have a couple of different horses? And if so, can you level up (feed) more than one horse per 24h or is there a one feed per day restriction no matter if you have more than one horse?

I dont know if u can feed one peer 24h or* each one peer 24h, I think first one but good idea will be have pack horse and speed horse. I suggest to make your first horse that will be 1st tier as a pack horse than get money and prepare for late game and get tier 2 speed one.

I think the main purpose of having a horse would be speed... but I also like bag space. So it's a decision of finding the right balance, or having separate horses for the task. If it turns out that you can only feed once per day it'll take quite a while to level up 2 horses.