I've been using my 37C lately so I'll answer.
1 - I ususally find the slant to be quiter than other razors, but it often depends upon what blade I have in, which brings us to...
2 - I find that mine is better with the sharper blades. Astra, Swede, Feather. I did try a 7 O'Clock Yellow in a 39C i had and it worked well, but I generally don't get on with them.
3 - It's worth trying a Feather in it, especially if you already have some. If it works for you then great. I find that I can't perform more than 3 Slant/Feather shaves without getting a bit sore.
Ian