Its hard to say. Kiwami has less content than Zero and is the “worst” out of the 3 despite still being great, and going from Zero to Kiwami can be considered a huge step down.So I've never played a Yakuza game before, do I start with Zero, then Kiwami, then Kiwami 2?
PC only.
Personally id recommend Kiwami > Zero > Kiwami 2 but you do what you prefer. Kiwami is the first game tho and is still good for first timers.