I use a Subtank Nano on a Cloupor mini 30w and that fits perfect. Personally, I prefer regulated over unregulated, but I do have a dripper for those times I just want a good solid vape.
Your question, like others have said, is very subjective. It's more of a personal choice of style. Some like copper, some like small, some like big mechanical box mods with bombshells on it... it's very subjective.
The Kbox was designed for the subtanks, it's regulated. I'd probably recommend something designed for 22mm... which is most mods but the mini. For a mechanical mod, my preference is the Caravela full set. I've had it for over a year, and I still use it. It's a rock solid reliable mod. For regulated, my preference has been the Sigeli 100. That also seems to be a rock solid regulated mod as well.
Just for reference, here's my four "regular" mods... I have more, but these four I use regularly, and in these setups.
From left to right... Cloupor mini with subtank Nano (a good grab and go setup), Sigeli 100 with a fogger V4.0 (very reliable, and my @ home device), A Nemesis Clone + magnets + Kick W/squape-R For when I want to feel old school (I even use Silica in that build), and last, my Caravela clone w/derringer (solid performing drippe).
Not feeling the need to buy anything else.....except a subtank mini for a grab and go atomizer solution.