510 probably has the greatest range of manufacturers and ohms of all the units out there. 3.0 ohm + works fantastic all the way from 4.5-6 volts. There is a balancing act when it comes to ohms vs volts. If you use a higher ohm cartomizer you pump the volts up but it nets out about the same result as using a LR with lower volts. Big difference is that the higher ohm ones do not burn up as fast as the LR ones.
I know you don't like the CE2s, but bang for your buck wise they are hard to beat. They have incredible vapor production and flavor with lower voltages, but if you can go above 5 there are plenty of options. I need a HUGE capacity for
vaping while I work, so I use a MAP tank (5ml) on top of a Provari. The MAP tanks are built around a CE2. If your wanting something with a decent capacity and still have some flavor CE2r4 XL or MAP or Stormy tank or Giantomizer is the way to go. The little EGO T-tanks are just not the same.
If you went true VV, you can make just about any range cartomizer work from any manufacturer. People are selling all kinds of "special" cartomizers and atomizers to squeeze out the best performance from their weak bat mods, but you are not in the same boat they are now. You can crank up the volts, most of them cant, so have to order from someone like Ikenvape or the 20 other sites that say they have something special. Go VV and vape any cartomizer you want 8)