If you have two accounts, a margin call in one does not affect the other. At IB, I have no idea what they do. As futures can only be traded in a segregated Futures account, every other broker that does this moves money into a futures account, but because of the way the accounts are linked, I expect you can't trade in either with a margin call in one. With us, you get two accounts. The margin account can't open with a margin call but the futures account can continue to trade. Same with a call in the futures account, the margin account can still trade. I would prefer two if I have the funds to fund two. If not, you have no choice. For those at IB, what happens if your account has $40,000, and your futures requirement is $20,000. Can you still DT in the margin account as there is only $20,000 there if they move money to a seg account, behind the scenes?
The answer is no, Bob, you can no longer day trade! I have a small account here mainly to trade overnight options in the SPX, as they are the only ones that offer it. When I traded some futures recently, the margin used for them brought the account below 25,000 available, daytrading was restricted.
Ha, that's why there are opportunities there! The SPX options market between 2am and 815am et. When something is mispriced no one else is there to sell or buy.
a single universal account is 100x better, it gives you a lot more flexibility and more efficient use of capital
For a universal account with discount commissions, I cannot think anyone besides IB. You can transfer money between accounts at TradeStation from equities to futures (and vice versa) for next day trading, but ≠ to a universal account.