I've found the Kanger single coils usually do need a little voltage control. The 2.5 ohm coil should be fine with an unregulated battery but I haven't tried them. I've used the 1.8's and some batteries don't go down low enough, so use the 2.2's. Generic coils can also be OK but concentrate the heat more so have to be even higher.
It can also be good to use 2 such devices, after several hits they can use a little rest.
You didn't say what the cheap clearos were, but EVODs and some others can take the same coils as the PT2. It is possible to take these apart and remove 1 or 2 of the "flavor wicks" on top of the coil, to loosen the valve effect. I also rewick them (real Kanger coils only) with cotton, which is slightly better, even though this is always on an already used coil. If you try this, the coil is cleaned, after removing the wick, by dry burning, washing while still hot, drying, and dry burning again. Dry burning should only be done by pulsing until the coil glows, too hot or long and it will damage the silicone insulators.
Distilled water thins and reduces vapor temperature for VG. I think adding water and a few drops PG would do even more. I tried adding some PG to a VG + 5% water juice and its effect was magnified.
I'd rate the PT2 and EVOD as follows:
Vapor amount 3 out of 10
durability 9
finickyness 4
tank cracker resistance: EVOD 2, PT2 10
flavor amount, per vapor: EVOD 11, PT2 6
flavor amount, total: EVOD 7, PT2 4
flavor quality: EVOD 5, PT2 8
(flavor, as always, highly dependent on juice)