I use a single 4" cube filter in my 10g tanks (including one crowded platy fry tank) and a pair of them in a 20g tank. They do have larger ones for bigger tanks, but I have no experience with these. It definitely wouldn't hurt to put a 5" cube filter in a 10g, beyond the space it would take up.
I would go with 20ppi and no denser since these clog up much slower than 30ppi on up. Most of mine are 30ppi, but the last two I ordered are 20 and the one I'm using is definitely lower maintenance. The trade off, of course, is less bio filter surface area. My fry tank has 30ppi foam.
The only benefit of the jet lifter, as far as I'm aware, is redirecting the current horizontally. I prefer the jet lifter over the standard lifter, personally. You can really tell the difference in current.