Docs: https://github.com/Payum/Payum/blob/master/docs/payum-vs-omnipay.md

If our systems like smashpig or other systems disappeared, would this be the right choice or would we build our own again?

Fill out the spreadsheet:
https://docs.google.com/spreadsheets/d/1VXzwqtCjn8lJ5WdknafaYkm9Eba5sQJmvm10GFCbOGs/edit#gid=0