bonus added into our equity, and it will supported account for extra margin added. and from my earlier post, not all bonus also suport for stop-out calculation, those kind of bonus only support for entry trade.
simple case : I've got 15% on tickmill bonus while deposit 1000 USD, my current equity now 1150. example I spend 100 USD margin used for trade, at this rate the stop out level are 1150-20 = 1130 since their stop-out are 20%.
compare to any bonus which doesnt added to SO calculation, said we've got 100% bonus, current eq. 2000 USD, same margin used 100 USD, the MC level would be at 1000-20 = 980, since those bonus are only for new entry.
and based on my experience, STP brokers wont offer unreasonable bonus such 100%, because these would harm their own unless they're MM brokers which literally mean not STp one.
hope it helps.