Us there a way to know how to balance a fight? In 5e you have a Challenge Rating that let’s you know roughly how tough a creature is and how many a party can handle (ok it’s far from perfect and doesn’t work great, but the concept is there). Is there an equivalent system for STA?
A sneak-in question for clarification: When you have unbalanced encounters, do you take turns until everyone on the smaller team has taken a go, then have the remaining memebers of the larger team all take theirs?
To illustrate: Team Letters has 5 members and are having a skirmish with Team Numbers who has 3 members. The turn order is:
Round 2 - starts over again.
Challenge Ratings in D&D (not only, but also 5E) is necessary, because characters undergo lots of “vertical” character development: Stat points rise, sum of stat points rises.
In STA, character development is slow and often more “horizontal” (points change, but their sum does not) and only once in a while “vertical” (points rise, their sum rises).
Since characters do not change too much, you don’t need too much balancing beyond the “Minor/Major/Notable” NPC classification. Have a look at p. 299 f. of the Core Rulebook for balancing combat encounters (find some numbers on p. 300).
For encounters with more/less NPC than PC, have a look at initiative description on p. 163; especially the last paragraph on that page.
Fight is short and can be deadly. The best prepared team wins.
Cautious players take support characters with them.
As a GM, you can spend threat for reinforcement. So no need for an overpowered encounter, adjust on the fly.