Once I select the Cross-save option (I also have PS5 copy) game crashes.

After that it crashes every time right after Larian logo, so no way to uncheck this option.
Only deleting "Baldurs Gate 3" folder from Documents/Larian with all the game user settings hepls to resolve this.

have you got mods?
Playstation does not allow mods so you can't transfer saves from that to PC if you have any mods because those save games say i need X to load

Nope. No mods

Managed to resolve it and the issue definitely was connected to my Larian account and old EA saves in cloud.
Once I disconnected it from GOG and PS it worked fine, if connected back it still crashed. I deleted my Larian account and made it again with the same email. Everything worked fine, but didn’t want to sync saves.

So, I deleted it again, made an account with different email, reconnected GOG and PS and voilà - everything works and syncs.

Sad it doesn't just say "hey you got bad email, do another one" instead of crashing on loading

Just deleting the EA campaigns would have worked as well

Like the instructions said.

RTFM, right?