Mostly I click on the Squadmembers, EXCEPT if they stand very near together

If I have 4 Squads near eachother and want to split them it gets messy. My tip: dont try to select more than one Squad at once. Just click every single one and give the order.
Don't try to select them with click and drag. It feels amazing if you manage to select exactly the Squads you wanted, but for me it almost never works on the first try.
I think you will get used to it with a litte bit of experience

. It is sometimes... confusing. Sometimes the Squad is pretty spread out (for example if you retreat, and one of the members gets blocked by a tank).