+1 for Mimestream here. Been using it for almost a year and it's incredible. The developer spent over 7 years at Apple working on Mail and Notes. If there's anyone that's going to be expert at creating a "native-like" experience for Gmail on macOS, it's this person. The results speak for themselves.I use the stock Mail app and find it works just fine for me.
I have, however been beta testing a Gmail-specific client called Mimestream and like it a lot. Not sure when it's coming out or what the pricing will be, but it seems to be in really solid shape and has been in beta for quite a while. No support for other email providers, unfortunately, just Gmail.