Okay, so in the lake near Covenant, there is a set of power armour underwater. What type of armour it is depends on your level at the time of going there. My question is, if I already went to the set and it was T-45, if I don't loot it and I come back at a higher level, could it be a different set?

Nope. It locks in when you first encounter it.

What if I never went in the water, and never saw the set but was in the location?

how do you know what set it was then?

How does this work?
Cells reset and I guess its then level scaled again.

I just found a near-full set of T-45 power armor that is near Tenpines bluff. I was level 54, and didn't even know it EXISTED until I stumbled accross it. That cell originally loaded when I hadn't passed level 10, having gone straight to Tenpines Bluff after escorting Preston and Co. to Sanctuary hills and accepting the first Minuteman mission..

again, how does this work? you can't undo it by loading an older save file...

so where does fallout 4 "store" such specific information about whats spawned in new cells?

Actually, you can. So long as the older save pre-dates your entrance into the cell. Some of the suits of PA- which are in buildings- can be save-scrubbed this way. So long as you don't enter the building before it spawns the PA you want, you can save outside the building and then reload until you get the peices you want.

As for where it stores that info... hell if I know. I'm just stating what I've consistently observed.

That must be why I just found my second T-45 set next to a pre-war crashed vertibird fairly near the Red Rocket at Level 53, I missed it on earlier trips through the area.

why not just go get x-01?

nice jetpack you have on your avatar^^

You... misunderstood the thread. You need to be a minimum level of 28 to get the X-01 to spawn, otherwise it spawns as a lower grade of PA.

And the suits don't re-spawn or re-level if you load the cell they're in.