8gb is a decent amount, enough for an environment and a few characters maybe. I say maybe because everything is subjective and depends on quite a bit. I have a 1080 and a 1070, both 8 gig cards and sometimes I can fit 3-4 characters in an environment no problem and other times I can't even render an environment by itself without Daz dropping to the CPU due to the way textures and things are set up (in that case, use scene optimizer).
Benefit of the RTX cards is the new tech and all that, but you're paying for it. RTX is enabled in Daz now so there should be nice boosts.
EVGA is a good company and I have many of their products. Honestly, I don't think you'd go wrong with EVGA, MSI, Gigabyte, etc. They're all pretty big.
One thing you may want to consider is looking for a used 1080 or 1070, or even a 1060 or 2060 or something. Amphere is around the corner and those cards should come out next summer. If you can wait that long, the rumors are they are going to be pretty powerful and slightly less than the RTX cards so that may be a good time to really upgrade.