I should clarify, I can actually get considerably thick clouds at level 3 or below, first hits no less, but that is with this usage style: (medium fine ground lemon meringue, probably under .1g)
When using the cooling unit, it makes sense to start higher, as you may see thinner vapor (perhaps losing some in the cooling unit when starting that low) but I still enjoy milking the low temps. I also often load less when I'm using the cooling unit, so that also means less clouds.
Point being without the cooling unit and a decent load, I can get fairly thick hits even at level 3 (thinner yet still visible vapor through the cooling unit too), and those flavors, my word!
Bumping up to 5 or 6 sooner, can choke me with vapor, through the cooling unit... Temp stepping from low, I typically won't get much more out of finishing at 8 instead of 6.5 in my experience.