Well, I guess we are missing a lot of information. 20mg Freebase ought to be causing you to cough your head off from the throat hit alone. 20mg nicotine salts or nic-salts won't give you much of a throat hit.
"Normal" percentages would be 70/30 VG/PG mix or 80/20 VG/PG. PG being most flavorings, PG, sweeteners and such, and the nicotine if it is in a PG base. VG would normally be just the VG, although many folks do get their nicotine in VG. Note, PG helps to add throat hit, along with nicotine.
Now, for me, I use a 3mg mix for 80/20 VG/PG using 100mg freebase nicotine in PG.
For a 100ml bottle, that's 3ml nicotine, 12.5ml PG, 4.5ml total in flavors (20ml total), with 80ml of VG.
If I wanted to raise my nicotine to 5mg, the numbers would be 5ml nic, 10.5ml PG and 4.5ml flavors (still 20ml total for PG). If I wanted to go up to 20mg nic, I would have to switch to 75/25 or 70/30 VG/PG
I personally do not get much of a throat hit from 3 or 5mg mixes, but then, I started with 48mg freebase due to smoking little cigars back then (coming up on 10 years ago now), and right now, that is perfect for me, in my .5 down to .17 ohm coil setups, at 35 to 50 watts. Squonking, pods and Single and dual coil RTA's.