Most serious competition clods are running 120a sensored hobbyking esc's. Motors are usually where people change it up with Reedy, Orion, Trinity, Trackstar, Reds, Etc. Motor turn depends on manufacturer. Some companies 8.5t is another companies 5.5t. Its kinda hit or miss. Stick below 8.5 and above 5 for solid race truck speed IMO.

There are two ways of going about setting the ESC's up. Either through radio mixing or through a y harness. Mixing is usually trickier depending on radio but cleaner for wiring, where as the y harness is easier but messier wiring wise. Done right the result is usually the same. Mixing has some other advantages but dont ever seem that necessary in my opinion.