Some thoughts I had while playing today:
1. VATS drains my power core too quickly. It's pretty strange how my pip boy can power the VATS thingy forever (I believe that is supposed to be the ingame explanation of the feature), but as soon as I input it into the Power Armour it starts using battery like crazy. Maybe if you actually got any VATS-related bonuses for it...
2. I realised that if you pass by an cell close enough, but don't explore it because you're already 500 kgs above the limit and leaves it to come back later, all the corpses in it will despawn with time even if you haven't actually been to the cell itself (presumably because it was loaded in the distance?). I weep for all the fat lutes I have missed out on because of this.
I don't even try to make sense of the VATS, it doesn't fit any kind of logic or lore. As for the power armor, their cores were supposed to last for centuries of actual usage, in fallout 1/2 lore, if I recall properly.
Also AP is used when running, and something like the piezonucleic PA chest can help you recharge it faster, but power armor doesn't give you infinite AP, although it is powered by flipping fusion. In the end, it's all game mechanics so I just ignore it.
About that cell loading, it's also source of endless woes for me, I often find dead hostiles when visiting new places, and it's really frustrating that I couldn't be the one killing them. Often, I hear shooting in the distance and I go there and kill everyone but I'd rather not be forced to visit those places until I want to. Not to mention that there are areas so packed with such encounters that you could do this all day (and obviously you'd become overloaded quickly, forcing you to go back, and lose loot/xp...).