Chose the "Subtle" approach and had to skip the gun fight part after like 10 tries. I took Packie, who I had maxed out, as one gunman but cheaped out on the other and he always died immediately and I got overrun. At one point I only had like 3 enemies left but switching to Franklin caused Trevor's "warning" on the character switch thing to go off and vice versa, and I eventually died via headshot. Definitely want to replay the heist with a different crew and try the other approaches.