I currently shoot the Canon EOS M6 ii (since Dec 2019). I have both the Ikelite and the Seafrogs housings. Before the M6 ii, I had Canon G7x ii and before that the first Olympus OMD EM5 and before that the EPL-5. I use the following lenses on the EOS M6 ii underwater:Canon EF-S 60mm macro (80% of all my dives)Nauticam CMC-1Laowa 65mm 2x macroCanon EF-M 11-22mm Tokina EF-S 10-17mm (Got that used here.)I used the 6" dome for both these lenses but the 8" is better for the Tokina.To address your questions:1) yes, I have used the EOS M6 ii underwater a lot, more than 300 dives.2) I like it but I also think there are better options in 2021 as opposed to 20193) I shoot strobes on full manual. If you set the on camera flash to minimum power, I feel you can get off a couple of shots per second4) I think the IQ is very good. Not as good as FF but better than my G7x ii5) I have the Canon adapter for EF lenses and it works great with both the 60mm macro and 10-17mm TokinaIf you are on a budget, I think the Olympus EPL-10 packages are really great value. I also used to have YS-110a. One finally died last year and I gave away the other. I would seriously consider a whole package super deal from the classifieds.