pg will carry flavor better, and does produce a slightly stronger th, it is also thinner so the more of it the faster the wicks can carry it to the coils to be heated and turned to vapor.
vg some will find sweeter and will mute flavor very slightly, reduces th compared to pg, and being thicker also makes for nice clouds. however being thicker will take longer to get the liquid to the coil.
some where between 80pg/20 vg and 20pg/80vg seems to be most peoples happy spot, however there are those that have pg or vg allergies and need to be closer to 100% of the other one they can use.
now your issue may not even be the juice or the battery. The 18650 and 18350 will supply the same amount of power, the 18650 may do it for longer. One thing I have noticed with the k100 which is currently my mod of choice is the 18650 will hit harder, I have noticed this in general use and by checking the voltage drop. Something about the tube being fully extended allows less of a drop its very minor but .4volts makes a huge difference in vaping of about 1 1/2 watts which is a lot of heat difference. A kick can help fix this problem as you can set the wattage to what you like only down side is it wont work with the 18650 in the k100.
now the other thing I have noticed is that some devices where the air holes are located by the threading below the base they get blocked on the k100. This will affect the suction needed for wicking. You can try using a 510-510 adapter they are cheap (under 2 dollars) from most vendors. this will raise the tank up a bit and may help. combined a reduced air flow, slowed wicking and more power and its burnt city.
Not sure why such high VG. Did some research and read for protank mini top, better with more PG than VG. I am still really clueless of whats the difference... Supposedly for fatter clouds? Better throat hit? Maybe u can help me understand. LOL. Even when I used the 99 %VG the wick was pretty absorbed...
I have tried the cold hit... With the 18650 battery was still burnt tasting.. Threw 2 coil units out... Hmmmm.....
Deleon, possibly the best explanation yet, gotta bookmark that one for later.
Since I diy my own I get to play with pg/VG blends and have found that for me 80% VG works the best but anything above that seems to clog up most coil heads in most tanks. I use a dripper/RDA so it doesn't make any difference about the VG content as far as wicking but I have noticed that the thicker the liquid (higher VG content), the less the liquid will transfer through the wicks.
Ann, as far as the pg content helping with with the production of fatter clouds I will have to disagree. If you watch the YouTube videos of the "famous" cloud chasers (mcvapes, rip trippers and so on) most of the time they are using a primarily vg-based liquid. Now, with that said, it is possible to vape straight pg (I have used it at times to help clean wicks) I just would be careful as I wouldn't want to be inhaling it all day.
The first question about pg/VG content I would ask is if you need the throat hit (something like a good burn from drinking alcohol) to enjoy your vape. If you need that, you will want to have a higher pg content then you have now. I would suggest that you check into some sample size bottles in different blends (ie: 80/20, 60/40, 50/50 all in most VG/pg notation respectively) and see what works best for you.
With a pro tank the wicks are very small and most of them cannot even be seen unless you take the head unit apart (see Grimm Green's rebuilding a pro tank coil for more detail on its construction) and I would not recommend rebuilding one to a beginner, but it may help explain how things work "under the hood" as it were.
Speaking from personal experience, the cold hits (sucking on the mouthpiece without firing the battery and used, among other things, to help try and prime the wicks in the coil head with juice) do tend to have a strange taste, but it isn't something I could call burnt as the coil has never been heated at this point.
Something else you might do is to use a "primer puff" before you actually take a puff of the pro tank; meaning, fire the battery and take a very small puff and blow it right back out (while letting go of the fire button) and then going back to hit the device like you normally would can help with getting more juice to the coils through the wicks.
Since I use a kamry daily, let me dive into specifics that might help you just a bit, I'll try to keep it simple.
With an 18650 battery on the mod you are firing the coil with 3.7 volts from the get go and there is no variation in power output (unless you add a kick, its what the kick does) except for the drop in power as the battery runs down. Now, that 3.7 volts should perform the same as any other device that is firing at that power setting (some seem to "hit harder than others but that's outside of the discussion here) and with a pro tank at 2.2 ohms (single coil) you shouldn't be getting a burnt taste or dry hits. However, the more I think about it, the more I think I know what is going on.
A coil (any style, in tank or rba/RDA, cartos too) takes a short amount of time to heat up, meaning that unless you are prepared for it (primer puff, short pulses while it heats up) you are most likely pushing the fire button and holding it until you get the hit you need regardless of the time needed. That is one of the pros and cons of mech mod (no electrical restrictions) but also something that you need to keep in mind when using a tank on a mech.
The coil will fire until the wire snaps as long as you are holding the fire button, which can cause the coil to run dry if it is not wicking properly (no matter the reason).
What I would suggest is to do a few primer puffs until you are getting decent vapor production, which means the coil is sufficiently hot and you have a decent amount of liquid on the coil to keep it from burning hit wick. Once you get decent production then you can take a puff like normal, remembering that a puff for longer than 10 seconds increases the chance of running the wick/coil dry and burning the wick (one of the reasons many devices have an "overtime vaping protection" which just shuts off the battery after 10 seconds to help you not burn the coil or damage the battery) and keep in mind that the 10 seconds is a pretty big hit, even for the cloud chasers.
Sorry the reply is so long and I hope it helps with the issue.