The Lua reference from boxmein has been down for over a year now. There is a copy of it on wayback machine

The Wiki is definitely more comprehensive than boxmein's reference at Lua. The wiki is mostly complete, covering every function, including the new functions and changes in 95.0/96.0. It does miss the platform API for some reason, but boxmein's reference didn't have this either, because of how old it is.

boxmein's reference had a few extra things documented, most notably tpt.el which the wiki doesn't, but the wiki covers the modern replacement of elem.property and elem.element. The only other reason to use boxmein's reference is because of how pretty it looks. But you should always use the wiki instead because it is actually kept up-to-date with the latest changes to TPT. You may also find this reference useful, it covers Lua, a bit of c++, and some other stuff: https://mrprocom.github.io/projects/tptreference/#welcome