Before coming across this video I did not know of a way to replace things over multiple files without relying on LSP rename functionality. Apparently you can grep -> send to quickfix list -> use :cdo to run a command once per match.

There's also this quicker.nvim plugin (same creator as oil.nvim) that let's you treat your quickfix list as a buffer you then can edit anything in there and afterwards save, similar to oil.nvim giving you a bit of a more streamlined experience.

I'm not sure whether I'll end up using it but the :cdo command will for sure come in handy!