Ring doorbell 3 plus power-AC or DC

Hi, I am looking to wire ring doorbell 3 plus with wired installation replacing existing doorbell. On install page it says the transformer needs to be 8 to 24VAC and apparently 40VA.Ring also sells power supply adapter which are DC output voltage and much lower than 40VA.1. Does doorbell work with both AC and DC or What am I missing here?...2. I have a setup with separate transformer and chime. Instructions say to simply replace existing doorbell with Ring without any mention of chime having to be compataible. I know Ring also publish a chime compatibility list. When wired to a trafaformer, does Ring work with any mechanical chime? Ta