Received my Colossus today , great razor. I went for the R1 plate, had heard it was quite aggressive for a moderate plate but this is not the case at all, it is definitely a moderate shaver and was much milder than my Ikon SB or my Cadet, gives a very smooth shave.
It is always comes down to YMMV:
For me, I've been using my ATT (5pc set) for the last month trying different configurations between H1, M1 and R1 baseplates. I've more or less settled on the R1 baseplate as my go to. I've previously been using Polsilver SI blades which proved a bit harsh for me. The last 2 weeks I've been using Wilkinson Sword blades with R1 and H1 baseplate and I've been getting some of the best comfortable BBS shaves consistently.
Trying out different blades highlights other traits in your razor (in this case baseplate).