Last MegaMek/MekHQ campaign, I went with 2 tech teams per lance (one of them Regular or Veteran, the other Green or Regular), plus another team (Veteran or Elite) at company level. If the unit had grown beyond "reinforced company" size, I'd have added a team for the second company, and then another team (Elite) at battalion level. The higher level teams get called in for the more complex tasks, while the lance level teams do the bulk of the work.
As pointed out, aerospace assets take about triple the amount of tech support, and one team per ASF is about the absolute minimum. Take a couple of hits to Fire Control or Landing Gear during a mission, and you're looking at several days of down time at minimum, with mediocre odds of success as a field repair, or else taking a couple of weeks (or close to a month for some jobs) spending the extra time to raise the odds. ASFs are "hanger queens" by their very nature, and if you're tying up a tech team for 2 weeks replacing a damaged sensor system, you're going to want a second team doing the armor repairs and routine maintenance in the mean time, otherwise it's another week until it flies again.
In contrast, one tech team can handle MOST of the repairs of a vehicle lance, although you'll probably want two, so one can do the major items, such as repairing motive hits and locked turrets, while the other does miscellaneous armor repairs and ammo reloads.