Rom Path is ur Roms that u want to inject SM64.
When u get to inject stage it will ask where u want to save the output Inject.
Ini is basically a configuration setting per Rom to make some not all work properly and some dont even require an ini and then there is the Builds FZeroX being the latest with most features via Ini but yet the odd Rom inject wont run with it so u can use a different Build.
Vessel.rpx is the name of Emulator and u can find it in Code folder in Base folder.
So if u wanted to use a different Build just stick to FZeroX since it being the latest Build and more Features improvements etc.
Then when Inject Complete u can just copy Vessel.rpx from another Base Code folder and replace the One from FZeroX which is there.
I dont pack my injects so I can Test with Cemu and Loadiine so it easy for me to swap between Builds via Code folder copy and paste.
I have done many during my research and I have gotten many Games to run that apparently could not but main problem with most is FrameRate.
Wii64 Rice by Fix94
Not64 GlideN64 only by Extrems
Use C2W Patch to OverClock.
and Injects via Virtual Console.
The Compatibility between them is not much different unfortunately but better than nothing.
Wii64 Rice good for Goldeneye.
Not64 good for Diddy Kong Racing.
N64VC good for main 1st party titles and quite a few others.
The Definitive Injector makes the whole Inject Process so much more convenient and productive including Widescreen Patching which can be a hassle for those unsure how to do so.
Take a look at my blog posts for more info they bit outdated for now with my current research but have valuable info to help explain things.
https://gbatemp.net/blog/core.456945/