Subtank mini is a solid choice. Has an rba section for trying to build but if you get fed up with it you can always put a coil head into it and try the rba some other time. I feel like the subtank mini is perfect for what your looking for. As far as a dedicated rta well... I WOULD have recommended a lemo drop rta but if your coil build isn't perfect/wicking you will have to drain the tank to get access to the rba deck for adjustments/rebuilding.
The morph tank is interesting. Not only does it come with adaptors( different chimneys and different base's) for different coil heads, but it also has a decent rba section. It's rba section looks much like a kayfun build deck and it's pretty simple to work with. Since it's juice channels are huge as well as the airflow you want to make a bigger coil with more wicking than an average rta.
I honeslty don't know of too many other rta's out there but the I hear lots of good things about the kayfun's. I hear their air flow is on the restrictive side, good if you like mouth to lung hits.
Have you heard of the gem rta? You should scan around youtube for popular rta's and you'll hear about the gem and the kayfuns for sure.