Since you've said this, I would want to say that the MVP 20W won't be enough long term.
It's an excellent device, I have one myself, but it's been shelved since I prefer other aspects of vaping. I like my hot, dense clouds.
I'm assuming what you said to mean you'll eventually explore rebuilding RTA/RBA's, and while 20-30W will be huge difference from what you're using, it really pales in comparison to what some of the other devices are capable of.
At the minimum, I would look for a 40W capable box (DNA40 is a wonderful chip), but preferably 100W+ (Sigelei and IPV come to mind) if cost is no issue.
It'll allow you to use any topper you can get at your disposal, from cartridge-based tanks to rebuildables at sub-ohm coiling.
You can experiment upwards until you find something you're comfortable with without having to keep buying new devices.
Toppers are another story, but once you find a style you like all the buying dies down a bit.
One drawback is most boxes use replaceable and rechargeable 18650 (sometimes other) batteries, but generally last long enough that you don't need to carry a bunch around all day. Another is the shape. Some love it, some hate it. But it has its advantages.
There are a few high powered mods out there that have encased rechargeable batteries, and a few tube-style, but the tubes generally lack in battery life.
Someone recommend the Kanger Subtank, which I think is right up your alley. You can replace the stock coils as they burn out while using the second deck to practice building when the time comes. If you don't like building, stick with the stock coils.
The Atlantis is another highly recommended tank, and you can rebuild the coils. That being said, you need to build on the existing stock coils, which can be a lot more tedious than working with a whole building deck like the Kanger offers.
Ultimately, it's up to you. Anything you do that's not smoking is good in my book.
Congrats on the resolution, by the way!
