Yep, Kleenstrip green leaves NASTY sticky varnish on pot.
Everclear will leave some light soot, more if burning with restricted air (rich).
SLX burns cleanest.
I actually often spike SLX (50/50)with everclear to up the ethanol to maybe 75% or 80% or so, still burns clean, but still lights easier than everclear, and has higher btu value than straight SLX.
The stove to pot distance that works optimally, ie efficient and fast, will likely be one that allows the flame to develop, and cover the most area on the pot bottom, without going up the sides (losing too much heat) . Just look visually.
My open cup burners (tealight) use about 1.125". It depends on how big the flame is, how big the burner cup is, and how large the pot bottom is.
Gotta add that bigger isnt better for the burner. A small tealight cup, works better on a small pot like fosters or SP600, than a large tealight cup. The large tealight cup works great on my evernew 1.3L. Of course I put a piece of bent metal flashing in the cups too to wick more heat into the alcohol, and speed up the burn. Cuts quite a bit of time off.