I looked through the rulebook for info on this situation, but it wasn't especially clear.

Can a Mech be a member of a CC capture formation if it's not the primary attacker? I'm inclined to say no per the rules for capturing, but I'm not sure.

Yes, only the primary unit has to be speed mode foot. Helpers can be any other speed mode that can legally do a close combat formation (no vehicles at all, no vtols)

And to add to his question, do the "helpers" have to take an order to participate?

Well, all members of a formation are considered to have been given an action, though you can order all of them with just one token. So if you have your capture squad move into base on turn #1, the next turn you can capture on the push, and give everything a click of damage and a second token. (or a heat, apparently)

If you fail on the push-to-capture formation, the primary attacker takes 2 clicks of damage; one for pushing, and one for failing to capture. The rest only take one, for pushing.

Unless the target of the capture was a mech in which they all take a click of damage for the failed capture in addition to any pushing.

I was all ready to disagree with you on that point, but on closer reading I discovered that you are, in fact, correct.

At my venue, we've always played it the way I described.

so do there orders count toward the total number of orders if they are helping?

No. It's just like any other formation order.

oh ok, thanks, because I have never tries to capture a mech, so I will try to use my EBAs or trackbikes for that now. Again Thank-you.

Note that the trackbikes are wheeled infantry. They cannot be the primary capturer, but they can assist.

Well, tracked actually, but that's splitting hairs on this point ;)