I haven’t decided yet. They both look good. Staggered is easy to do but like the rear tire ware and tire life could be much better on squared fit when you can rotate your wheels to give them an even wear. There is price as I’m sure I need some fender pulling on the front just to be sure there is no rubbing under load.
At the moment I have very modest 245/40-19’s square on 8” wheel and I wasn’t 100% satisfied with the rear camber. I needed little more to the back to get some of the nervousness of the car. In 540 there is a camber adjustment. I would say you have that too. You do have different differential and physical look is different so there is good chance that there is little differences between the cars. I always thought that M5 and 540 was almost same, M5 being the beefed up version and having more adjustments like camber/caster for the front. The camber adjustment is next to the differential in 540’s
It would be good to know how you go with 295 at the back. From my last set of Contis I got just over 40000km with regular rotation and I do have very aggressive driving style. I think that is the main reason I’m thinking of square fit is the tire ware. I did drive those tires up to 45000km till I got booked. The grip was just too good and getting better but the nice police man didn’t agree with me.