I looked into paying my DCU car loan through Plastiq, but because my DCU loan has a special discount APR that requires payment by transfer from a DCU bank account the car loan is marked as a "non-transactional" account, meaning it can't accept incoming ACH payments. I'm not sure how Ally works.
But, when you say "I was just approved for the Chase Sapphire Preferred" it kinda sounds like you want to use Plastiq for car payments to meet your spend requirement for the new card bonus. That's call MS, manufactured spend, using regular monthly payments to meet a spend requirement instead of actual purchases. MS discussion is not allowed on MyFico, and many CC issuers, particularly Chase, look out for that and if they catch you it can have unpleasant results such as denying bonus and even closing the account.
