Is there a maximum number of techs that you can hire?

yes, i think its 4 for drum corps and marching band and 3 for color guard and drumline

Correct, well to clarify for your Drum Corps and Marching Band you actually get 4 wind and visual techs, and 3 percussion and guard techs

For your Guard and Drumline, you get 3 techs of each.

Thanks.