I've been vaping DoggyStyle GTA tanks almost exclusively for quite a while now. I have two set up now, both on Pico 75's, using the same DIY liquid, the same coils and both coils are almost new.
With one Doggy almost totally empty and one just re-filled, I notice no flavor difference when I vape them alternately at the same power level. Doing this let's me try the same setup with only one variable different between them. The juice in the empty one has also darkened, but that should just add to any difference the lower juice level might create. My juice is 100% PG and about 1.2 mg of nic tonight.
I used a Genisis tank with mesh for about a year. The vape in that changed with an empty tank compared to a full tank because the wicking changed even when using the Genie tilt.
So many people report their vape changing due to darkening liquid or tank juice level, I can't help but think there has to be something to it. OTOH, I can't make it happen for me
It would be interesting if a few other people who have two identical tanks could try the same experiment