I vote for 2 but it depends on the faction/sectorial you play. YYs like mentioned above you can spam, same goes for Bashi. Aleph can run out of orders, if you take two or more. Sometime I will play my four Hellcats list ;.)
with tac sense and NCO you can now afford to have more hidden/AD models in your group and still have 9 orders.
I generally don't take more than two in a combat group, as I mostly run single group lists, but I have had 3 HD units in a single combat group work decently enough before, but those lists tended to have some form of order compensation instead, such as making use of the Lieutenants order. But 2 feels like a fair soft spot for a single group list at least. GRANTED the limit does depend a lot on how many of the hidden units are TO units and how many are AD units. Since AD units won't start generating their order until after the turn they reveal themselves, but TO units are more or less ''Irregular'' until they reveal themselves, so if you were planning on using them early on anyways, they haven't detracted from your order pool all that much. TL;DR: You can get away with three pretty free, but hiding a TO is less order costly than an AD. But ADs get to choose where to appear AFTER the deployment phase, so I suppose they are more adaptable.
For Ad troops in my main combat group? One, two if I'm being cheeky (and/or have something to stretch my orders out like an aggressive LT, LT2+NCO, etc.). In the secondary group, I will see nothing wrong with going for two if I have the points to spare. The secondary group is usually just pure fuel and it can house AD stuff as overflow to get shuffled back in to the main group as it takes casualties. HD troopers? I probably won't go above two of them in most combat groups, but for the most part they are much less limiting than AD troops when it comes to your order pool since they get to actually do something with their order when revealed. So sticking in three of the things in a combat group isn't out of the question (but rare for me as a Yu Jing player since my TO choices are all fairly pricey).
Double croc and a cutter is the most obnoxious I tend to go. I've had a double croc hexas specsergeant list before but it wasn't great. I much prefer HD over AD for the option to reveal my guys if I'm going second to get some orders on the table. I don't like feeling like im burning orders with AD troops off the table so I take 1 or none really. But I do keep losing to turn 2 or 3 ad troopers walking on the edge and scoring points so it's more likely my own poor play.
