I trade with WTS. groups like capital traders group, jc trading, principal trading partners are all WTS groups. You have to register with WTS and your deposit is held with them, not the group. The group usually gets a discounted group rate which they mark up to the trader (I.E. they pay .002 per share and resell for .004 or .005). I've been trading with WTS first through capital traders group and now on the WTS floor, never had a problem getting paid. My check is automatically sent every month on the 15th. I've never had to make the request. it's been a good deal so far.
The difference with the subgroups is that they put up their own risk deposit. they have freedom for setting pricing, but if the trader goes negative, wts will charge the negative account to the group until the proper legal action is taken.