would be possible to get my 90's computers and run erlang/elixir for a crypto node... or some version of it??

The page says their implementation requires 16 MB of RAM, so a late 90's computer could run it, but even mid-90's computers, like early Pentium models, often came with less RAM than that. If it shipped with Windows 98 or later, it should have 16 MB.

Yes - Erlang/Elixir wouldn't be the bound here. 90s hardware is plenty for them. They were designed for far less.