The vivis are cheap and very good. I am a fan of the mini and the tank. You might consider wrapping two 1mm hemp wicks with 32awg kanthal. I just hold them together and wrap loosely by hand. It produces a oval coil that has great vapor and taste. It's worth the experience imo. The Hemp holds out much better than any cotton I've tried. It will even withstand some dry burning to a point. Not all hemp twine will wick very well, and some has wax in it. Here's the best we've found so far:
Hemp Twine Cord 1mm 20 Test 5 10 or 25 Yards Color Selectable | eBay
Of course "natural" is the color a vaper would want
I've tried AGAs, (Tiamat and the Hydra). They are okay, but I don't care for the "cold" vape they produce. The Smoktech "R" is a good one for ease of use rebuilding. Not so sure about the longevity of this device though. Not a bad price at 17USD.
The best vape I've ever experienced is with the Terminator. It is a clone of the Odysseus. I tried to get an "Ody" but they are hard to find and are no longer being made. I've seen damaged ones sell for over 200 on the classifieds. Since I picked this up, all my other attys/RBAs are collecting dust, except for the vivis that I take when travelling. The copy of the "Ody" so well done that it has all the quirks of the original. It's not as easy to "coil and go" like the Vivi, but well worth the trouble in my opinion.
I believe the Vivis's design is based off the Ody to a large extent, just minimized. So if you want the vape style of a vivi, but the longevity of a true rebuild-able, the Terminator is what you're looking for. This is not a beginner RBA by any means.
I got mine from Stormy's vapor cellar; a registered supplier here on ECF. Faaast delivery and excellent service. I am not an affiliate, just a customer!