I am. Especially since I don't use drippers. I have some of those but don't use them for testing because stuff always seems to taste different in drippers.
Likewise. Imo, ALL tanks / toppers will affect the taste. I use pretty much exclusively the venerable KF2L and the Coppervape Skyline, which is pretty similar. They're what I use, so I use them for tests.
New recipes, or new sfts, get a 10 ml test. That gives me about 2 1/2 tanks, enough to know. (And yes, there have been a couple times that 10 mls was too much!

I did something similar with butterscotch's, caramels, vanillas and some other flavors. With each one I had a base and then started trying out different combinations.
Yup, another good way to test