You are in luck my friend, quite coincidentally i'm putting together a guide on the kit right now, the TTS instructions suck and leave out the hydraulic clutch, traction fluid circuit etc etc. Hit a bit of downtime with back problems so I can't do much these days.
Re the clutch side controls housing, you do indeed have to hack it up;
Then sand it down to smooth and either paint or powdercoat.
If you have or want to have heated grips, you will have to drill a new hole for the cable too, as the TTS clutch lever bracket covers the OEM hole.
You also have to make a short adapter wire. Female spade both ends, you can then connect the OEM connector to the TTS clutch switch. Either than or hack up the Triumph wires and put female spades on, would end up neater but is not reversible.
Re the tensioner pulley, the inner part is slightly wider than the outer part, the outer part should turn ok. If it doesn't you could take it apart to investigate, or send back.
Re the front cover gasket, the instructions say to use high temp RTV silicone on both the mating faces, and also the paper gasket. I haven't done so myself but reckon you could get away with just the high temp RTV silicone from the local auto shop.