Tickets from 3 party with reservation sytstem?

I’m not an AP holder and have purchased tickets in the past from a third party (i.e., Undercover Tourist, etc.) and have never had trouble linking to my MDE account, etc. But with the new reservation system and not knowing if I will want to reshuffle my park days and corresponding reservations (if available), should I get park tickets directly from Disney or are 3rd party tickets flexible and compatible with reservations and any subsequent changes? Thanks for any info!

I bought mine from Boardwalk and have had no trouble picking or changing park passes.