Having participated in a lot of them, it really depended on what set the boosters were from. Later on, each set had a few uber-good unique mechs that would almost guarantee victory. For the early and mid sets, if you could get a 3 cap transport from one booster and a hard hitting tank in another, mechs aren't as necessary. Also, some of the really good artillery can be more desirable than the mech in a booster.
As a practical matter, for the post-AoD sets, we just assumed that the pilots/gear cards in the booster went with the mech. The faction perk / alliance cards were separate.
IIRC, for pre-AoD, 300 pts was the normal force size. Post AoD it was 450.
