Coil placement relative to air inlets can affect TH as well.
Very true.
With an RDA that uses air intakes in the side of the top cap, you can rotate the top cap to adjust TH.
In an RTA, you can change the height of your coil above the air inlet to adjust TH.
As others have suggested, you can also add VG to soften TH, but you're basically diluting the liquid so you're diluting the flavor as well. You also have to be careful when adding VG to a liquid you're using in an RTA as it will "thicken" the liquid and can lead to wicking issues which can cause dry hits.
Another option is to buy another bottle of the same flavor in 0mg or a lower mg and mix the two. It will lessen the nicotine level and TH without lessening flavor.