RE: Can you freestyle with a Carve?
Well that's an interesing twist - a freestylist recommending the S-type over the Flare!
I think that shows that in good hands one can do darned near anything with any board.
As to the comment you've heard that such and such a board is "too fast" - that's almost an oxymoron in windsurfing. In the vast majority of maneuvers (well, FS maneuvers get invented every 5 minutes, so I'll discount those) you almost can't have too much speed. One can be going too fast for a specific maneuver at a particular moment / place, but the sailor can control the power, you know. Going fast is a CHOICE.
Now when you WANT to go fast, some boards will get there and some are just slower. Pretty much all the boards are fast enough; Ola's point that the Flare (and a lot of FS boards) have slalom-type rockers points out the need for speed in freestyle. Compared to years past, even today's wave boards scream - one can't forget Robby Naish's point that "The faster you go, the higher you jump".
So now you have 4 great choices in *B:
Carve - ease of jibing
S-type - quickest, most versatile, but harder to jibe than the Carve
Flare - dedicated FS board, a tiny bit less versatile per Ola
Kombat - great in waves, good all-around one-only board
I've never sailed the Exocets so i can't vouch, but the reviews are great and these days it's hard to make a mistake.
Enough. Pick something and go!