For an RTA, I would suggest the Smok TFV4 with the dual coil rebuildable deck.
I'd second this in that even if you screw up your build you can slot in premade coils to continue vaping on while you play with your coils. I think that's a solid perk of this tank.
As far as RDA or RTA, well, you can get RTAs with large building decks like the Crius's 3rd version with the Velocity deck, or you can get a lot of different RDAs with the same size deck. Bigger decks are certainly easier. The question is, do you want the deal with dripping or do you want the convenience of a tank?
Want a tank with a large deck, the new Crius with the velocity deck looks to be as good as they come
Want an RDA, well there's tons with nice big decks that should suit you well.
Want something with versatility and the TFv4 is your man.
I'm a big fan of the TFv4, but I will never claim it is the best at anything, other then versatility. Single RBA can be anything from a high ohm build to a low ohm wicked vertical coil build (guide on that on this forum). Want a solid build and the dual RBA is just that, really can't say anything bad about it. But, the decks are bigger on devoted RTAs. And RDA's certainly have easier to handle decks for the most part. But, again, it's nice that I can slot in the quad coil when I have screwed up a build and still fill the tank and head out for the night knowing I'll have something solid to vape on. And that's the strength of the TFv4 versatility and convenience.