Recommend you stick with 20mm stagger on the same profile (2x5/35R19, for example) to keep stability control (DSC) from kicking in more frequently. It works off of wheel speed sensors and when you change the rolling diameter of the wheels it cuts in more.
Yes, 275 will be taller than 265 but the difference is miniscule. Either get stock (245/265) or if not available plus 10mm (255/275) which I know they have in the Ventus V12 Evo Hankook tire that you're talking about.
Continental ExtremeContact DW's are also good riding street tires. Just drove another M3 Sedan on 19 ZCP's and it rides really well with the Conti's.