I'm sure someone who knows Canon lenses will chip-in - but one thought: the EOS Rebel T2i is, I think, an APS-C size chip, i.e., not an "FX" type sensor the same size roughly as 35mm, but slightly smaller.
Generally speaking, if you're relatively new to u/w shooting and macro, the advice is to use a shorter macro to start with on an APS-C camera. So (as a Nikon user) to start with a 60mm macro and then at a later date maybe move to a 105mm macro. The Canon EF100mm will be the broad equivalent of the Nikkor 105mm.
The longer macros are a bit trickier to use to start off with - and the shorter length gives good fish portraits as well as macro.
But doubtless someone will chip-in with helpful advice from the Canon perspective.
OP has a Sony RX100 compact. Where does the Canon SLR discussion come from?