Me I use an overflow. Just not a fan of drilling tanks. That tank you’re looking to move about 600gph. Jebao sells dc pumps that will move 400-1000gph. You set it to how much water to move. Good pumps for good prices. I’ve got 3 running now. One for 4 years without a problem. Running 2 pumps is doubling you electric. How big is your wet/dry/sump? I don’t use check valves. The sump is designed with an overflow to stop draining before the sump fill up. A bottom or side drilled tank will need a check valve.