I would just use one monitor. The actual “old school” method was using no monitor with the musicians playing softly enough to hear each other and the singer.
What’s amusing is people isolating drums and then adding delay effects which actually simulate bleed. At Columbia in Nashville, SOP was the singer directly in front of the drums using a cardioid microphone. That way the bleed was clean and enhanced the drum sound much like today’s “room” mikes.