is plastiq a good way to pay rent with a rewards credit card?

Yes, if your landlord will accept payment by credit card, and if you pay the credit card off in full every month so as not to incur any interest charges.

EDIT: now that I see your comment explaining what "plastiq" is (I thought it was a typo for "plastic"), then no. I'd have to get at least a 3.5% reward to bother with it, which I think is unlikely. Why would anybody pay that amount for that service?

Compare the rates. Usually, its better to pay cash.

They charge a 2.5% fee. Most cards cashback is 2% or less. Except for new card promos and things like that.

If your rent is 800, you pay 820. If you get 2% back, thats $16.40. Thus, you lose 3.60.

Yes.

Probably...but I have yet to find a landlord that accepts rent payments on plastic.