FWIW, i've brewed the Belle Saison twice and M27 once.
The 2 Belles (2nd was rinsed of the first) i started at ~20°C for the first day or so then ramped steadily to 25-6°C on day 3-4 (~50-60% fermented out). This resulted in 82% attenuation, and seemed to have a bit/moderate flavour impact.
The M27 was pitched at 25°C. It was ramped to 27°C the next day, then to 28°C the day after. 2 days later got it up to 30°C for 2 days, then gradually dropped to 21°C. This attained 94% attenuation (!!), the last few points of which were chewed out after it dropped to 21-2°C. Crazy attentuative power. I did a 65°C mash for 50mins that dropped to 63°C by then end of it, however i'd also accidentally hit 70°C while getting it to 65°C, so had to drop it down for the sacch step. It was probably at 70°C for a 5 minutes. I'm guessing that all helped achieve such a high attenuation, but i would've thought it'd just get an extra few %'s. The resulting beer had a moderate flavour/aroma impact from the yeast. Luckily i'd done a recipe that was quite malty and aimed somewhat at a Leffe Blonde, so it hasn't come out too thin, etc.
I was very happy with both yeasts, though i'll probably have a crack at the M27 in the next belgian attempt.
For doing the side-by-side, i'd maybe try pitching at 23°C, then move it up a degree a day up to 28-30°C. Seems a safeish way of doing it while still getting some yeastie goodness. Otherwise i'd start at 25°C, 27°C after 24hrs, then gradually up to 30°C. Its certainly fine for M27!
