Sizes of boots usually go like this: -
Pony/small- under 14.2hh
Small horse/Medium/cob - 14.2-15.2hh
Horse/large/full - 15.2-16.2hh
Large horse/x-large/x-full - 16.2hh up
You can find that this isnt always correct as some have short chunky legs etc but for the most part its a good guide. For a rough comparison my mare is 15.3hh, she is a dutch warmblood x tb, however she is very much tb in her legs and wears a medium/cob size, even though she is over 15.2hh (this is due to her canons not being hugely long either, you mentioned your tb having fairly short canons too)
I would, for everyday riding use some standard brushing boots, fore and hind if possible (woof wear make some decent neoprene ones). Then for jumping use either open fronted or close fronted tendon boots, bell boots as you mentioned, and fetlock boots on the hind (you can get some packs which contain both front tendon and hind fetlock boots, which may be useful to you!)
I wouldnt ever use polo wraps/bandages (especially if you arent experienced with them!) as they can be highly dangerous, I have seen a horse have such severe tendon damage from over tight bandages that it had to be put down....its so much eaier to use boots anyway and it is quite old fashioned to use bandages nowadays! If you need any more help or pics etc just say!
Hope that helped adam jumper!