A clamp marked as 30.0mm will most likely be a 29.8mm rounded up.
Salsa make some of the best clamps on the market, they round up the size in this manner.
It'll have a 68mm BB shell which means your SLX chainset will need 2 spacers on the drive, and 1 on the non drive side.
And they use a topswing front mech to clear the bottle cage mounts on the seattube. The multifit mounts have 28.6, 31.8 and shimless run 34.9mm. So the 28.6 is the closest fit that'll work. IME you may need to use only 1 shim on the mech for a perfect fit.