@xianc78 the plugin was one that would let me manually change the layer priority of tiles. normally, without doing the entirety of your maps manually (which is possible but more time consuming and would have taken me at least 4x as long), specific types of tiles are locked to specific sprite layers and there is no way to change them.
for these snowy mountain maps, i needed the tops of my trees to change to a different sprite layer, so i used this plugin. it was quite a while ago that i made this decision so i can't exactly remember what was going through my head, but the way i mapped everything actually turned out to not need the tops of the trees to be set to a different sprite layer after all.
my best guess is that i was thinking that i needed to have the trees go above this "shadow tile" that i use both to represent depth and cast shadows on top of other sprites (including the player) from things like second stories. the normal RPG Maker shadow tile doesn't affect much beyond the floor and walls so i had to make a custom one. since the shadow tile i made goes on top of the player, and the treetops also go on top of the player, i was probably thinking i needed a way to make sure the trees went on top of the shadow tile since the represented depth would be underneath them in some cases.
well, this turned out to not be true at all due to the way i actually mapped it out. it would have been if i was using VX or VX Ace, but since i'm using MV the layer system works a little bit differently. there is still a chance i actually needed this plugin somewhere else but it has been long enough that i don't remember putting it in, so i might just run into it in beta and have to find some fix for it then. i'm sure there are going to be a lot of things like that and it's just the nature of a solo dev working on something for so long with a lot of breaks and also improving along the way.
since it looks like i was only using it on these trees though, that hypothesis is probably the correct one. no idea why i thought that was the case. maybe it was while i was testing it out, but then when i actually mapped out things that changed. i haven't updated the engine or anything so it wouldn't be in that realm, but i could have sworn the maps ran fine right after i made them and that was on an older laptop so i wonder what the actual cause was or if i am just remembering incorrectly for some reason. maybe i thought it would work better on my PC but obviously didn't. the other plugins i added afterward don't seem to have any affect on the performance either.
still, i got it fixed so i'm not too worried about it.
@xianc78 i'm not very good at writing stuff on my own, but i am good at interpreting and editing code to suit my needs, generally speaking. i was getting pretty good with RGSS (ruby game scripting system, it's what RPG Maker XP/VX/VXA use) but then MV came out hahaha. I did make my own menu system for XP from scratch so that was pretty cool.
i'm not exactly sure what the plugin does because i haven't really looked through it, but i don't care too much because the problem i had was fixed and then some xD if it lags so much when there are a lot of tiles that have custom priorities it might be checking for those tiles all the time instead of just when it is supposed to draw them. maybe it could be fixed, maybe not, idk, but at this point i don't care too much because everything works just fine without it xD