Using the anonymized login function, you're limited to free ones only. You have to login with your Google account to be able to download apps you've bought.

Although I think that doesn't work for all apps, since apparently some require the genuine thing to register / activate and won't work with microG. No personal experience, just read that somewhere once.

Personally, I only use a single paid app through Aurora Store (Sun Locator Pro for my photography needs) and have only done that for two days now. Google hasn't banned my mint fresh account. Yet. ;)