I'd be a little aprehensive about running 2 seperate sump tanks with seperate return pumps. Say the first return pump quits, the pump in the second sump would pump all the water it can into the display, which would drain down into the 10g sump, which could cause an overflow. Also, if the return on the 20g quits, you would run the first sump dry, which if it empties enough, the skimmer pump may be out of the water for some time and burn up.
Those are the two worst case scenarios, but definitely two possibilities if you do run the seperate sumps. To avoid something like that happening, you could try to drain the display into the 10g, and have that suspended above the 20g, which would gravity feed the 20g, and just rely on one return pump. Some measures would need to be taken just so that if your return pump quits, the 20g sump wouldn't overflow, and if the display or 10g sump drains got clogged, they wouldn't overflow either.
It seems kinda like alot of figuring stuff out and playing with stuff and tweaking things. If set up properly, it can work well, but with the more seperate tanks that you add to your system, the more possibility that things could fail.
And, BTW, I don't currently run any sump. I don't even have my tank running! But when I set it up, I'm going to do a Herbie Style overflow/drain into a 40 breeder sump in a remote stand. I also am considering doing a BTA tank in my old 20g plumbed into the same sump. But the drain will hit the skimmer section, then that will dump into the fuge section, which will feed the return pump section.