What specifics per device are needed to "match" roms to attempt a port or create cust

I'm pretty new at all this buy the basics of installing already made roms I get my question is when attempting to create new custom roms what information about the device say (cpu, gpu, modem, kernal, etc) need to match up to attempt using or moding those said parts of the dev process in order to build a working tree. Continued below Sidenote........

Sidenote : idk if the terms I used were correct in there placement or meaning but I feel that any who will reply to this thread probably grasp what I'm getting at.

So essentially what I'm attempting to do is figure out what things to change and how to change them in order to figure out what goes into building a rom or the favorable option that I'm shooting for is what to look for to attempt to match up a already built custom rom from another device I need little to no changes in order to use on my device's, reason being, both devices I am currently woking on, which are a Samsung Galaxy Core Prime sm-g360t and a HTC Desire 626s, do not have a official or even, to my knowledge, have an official CM and honestly besides one,the HTC which I have TWRP and it's running now off the AdvancedStock rom I found on this site and it keeps wanting to break or just doesn't work the way I want .

ANY HELP IS GREATLY APPRECIATED

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