Either of the three sets above would do.
Irregular wars is a great set, but as you want to play GA you might have to find a way to manage Irregular wars unit bases. Sabots/trays would work fine though. Of the three sets I think it would need most figures, maybe only a little more..
Pikemans Lament and Donnybrook are similar sized games in terms of figures and have individual based units. Both are set after the conquistador period but the rules are pretty generic and both have tribal warriors so would work ok.
All three sets have little add ons - characterisation of leaders and random events which help add a little flavour. PL and DB are, perhaps, a little more flexible. I'm playing some mid-late 16thC solo skirmish games and decided on PL over the other two, which I both own.