TFV4 but with some of the lesser known coils, like the Beast coils. I have a quad Clapton coil going closer to 4 weeks than 3 now, which offsets the price of these coils. At 95w, it is a cool airy vape with good flavor and plenty of clouds. With a little online searching, the coils can be found individually. There are also 3 or 4 RBA decks available, including the RCA with a big, single, Clapton coil pre-installed.
For a cheap tank with coils that last and can be found anywhere, I'd mention the original Herakles, bottom-fill and all. But for 1 tank that can provide a variety of experiences, I'd go TFV4 (the full kit with the extra parts, in the larger 5.0 ml size).
The CCI Maus also interests me, but not at the $45 I am seeing now, plus another $20-22 for a coil pack. Maybe watch a couple of YouTube reviews to see what it's like...... though I take many of the reviewer claims with a grain of salt......every tank they test is "the greatest." The CCI Triforce seems popular in certain regions, not others. And the COV tanks, like the Vengeance, has its fans. These are cheaper than the CCI tanks, squat little tanks with big wide-bore drip tips.