[2020] Having trouble linking with Game Center. Apparently there is a lvl 3 acc there that I cant seem to get rid of. My main acc works without Game Center fine but I would much rather want to save the hassle of turning Game Center on and off for certain games.

If you already linked another account to that specific GameCenter account, you can't link your main account to it anymore (only 1 account can be linked to GameCenter).

The only solution here would be a brand new GameCenter account to link your main SWGoH account to.