I think the other secret techs are a little overshadowed on Amazon, BUT the generic Biomancer's Scan ability does lower damage resistance and status effect resistance at the same time, which is low-key awesome with Synthesis/Psynumbra which have a ton of status effects. Celestian/Voidtech are popular because the 1st secret tech unit they get is changed for amazon only to be mounted and they are definately better with 25 bonus HP on a faction that normally doesn't have good melee until it researches the lategame clone predator. Xenoplague is kind of a natural combo because buffs with the 'animal' tag effect the 3 xenoplague units.

I find Promethean comfortable with any race just because of healing and status effect removal on basically all your units from turn 3 of the game. This is basically an amazon specialty since you can get a +5 and a +10 from seperate hero skills AND a +10 from the doctrine.

Normally Army wide armor/shield buffs are better than HP buffs, but when you stack multiple of them HP suddenly become attractive

Planetfall age of wonders amazon