All 8 speed Shimano cassettes will fit on your hub. There was never any road/mtb difference for cassettes, except for the first generation of 10 speed cassettes.

Shimano road deralleurs are generally designed to handle up to a 27 or 28 tooth largest cog. If you switch to a MTB rear derailleur (8 or 9 speed compatible - 10 speed mtb rear derailleurs will not work) you can use up to a 32 or 34 large cog.

My 8 speed MTB has a triple crank designed for 9 speed chains and it works 100% perfectly with the 8 speed chain.