Is there a way to be signed into your broker & paper account and trade both? I believe I tried it once but dunno if it was allowed due to data feed restrictions. Maybe it's a failsafe to prevent trade errors?
Possible, but only one of them can use real-time quotes. The other one will be switched to delayed quotes. (I don't recall if there is a way to subscribe to real-time quotes for a paper account separately)
Yes, this is possible but I forgot the details of how to do this. In your IB account you can create multiple logon names. Each of these names can then have TWS/Gateway running. As @guru already mentioned might it be necessary to pay for data subscription for each of the account names you create.
I think most of them use delayed quotes of Papertrading. This is because real-time data is expensive I use TradeHawk for my papertrading and live trading
I wonder, instead of asking, why didn't you just try it with your broker? Or are you looking for brokers where you can do this? The question is too generic. Every broker is different. It is possible at TDAmeritrade. The quotes are delayed (for equities), but the trades are NOT! So when you make a trade, they will use the current price not the delayed one. The P/L will be out of touch until you close the trade. Futures aren't even delayed on the chart. So you can trade futures just fine, you get what you see. But there is a possibility of screwing up when you keep switching back and forth between paper and real account. If you are not careful you may execute a real trade intended to be a practice paper trade and then.... To avoid this maybe use 2 different computers. Or use a 2 step process when putting through the trade.
But the question is posted in the forum segment titled "Interactive Brokers". So I assumed it was specifically about IB.