Re: Migrate Sims 4 from EA Play to Game Pass
@matsmonsen If you've bought DLC separately, your account will own that regardless of how (or even whether) you have access to the base game. In theory, this process should work fine. In practice, it can be a headache, with people needing to contact EA support to get the EA Play version of the game removed from their accounts first. In fairness, this happens to people who buy the game outright too, although apparently not all the time.
I don't think you'd need to reinstall, but it's possible. No one so far has described the exact process to switching over. If you do need to uninstall first, make sure to back up the Sims 4 folder in Documents\Electronic Arts: this contains your saves and other user data.
By the way, have you considered buying the base game separately? It's on sale for $5 U.S. until tomorrow (Tuesday) morning. That way you could play even without a subscription.