Agree the dimmers are nicer for daily use and better value but you can't configure them to activate a lot of the labs scenes.
I use these: https://www.ebay.co.uk/itm/Philips-Hue-Dimmer-Remote-UK-Light-Switch-Adapter-Cover/253647681892?hash=item3b0e947964:g:ZQEAAOSwTM5Y19zp
Yes, Smartthings and the relevant DTH.
i dont like the design of the dimmer itself, i picked this up from argos a couple of weeks ago when it was 24 i think it was. It isn't worth the full price but im not totally fussed about what 'more' the dimmer can do. When the dimmers are made for UK size switches ill get some more of them.
How are you using your Xiaomi buttons? Have you got Samsung Smartthings or some other device to communicate with Hue network?