Ive never tried Carolina Extracts but have heard that it's excellent nic. I like NN nic and Vapertek regular nicotine, I think both of these are very good. I use nothing but nic salts these days though, I'm spoiled by their smooth vape. I mixed up some regular nicotine and I just don't care for it anyore, lol. I use 80PG/20VG diy, and the nic salts helps cut down on the harshness of the PG by lowering the pH and cutting down on the "hit" of the nicotine. I really don't think that for the same mg, I get more nicotine uptake using nic salts, to me its about the same. I think what actually is occurring at least with the nic salts I've used is that you can vape a lot higher nic concentration if you want with nic salts because it takes the harshness of the nic hit away, smooths the vape. I can't speak to the juul, I haven't used that and I don't know what all is in it other than likely benzoic acid from the patent info. I saw a test showing the juul nic concentrate around 60mg, no way you could vape that high with regular nicotine. Nic salts of course are made for pod type mods, or vaping at low power, I only vape around 2 to 2 1/2 ml a day, 24 mg nic salts in tanks at 11 to 12 watts, or in Myjet pods at 36 mg nic salts.
So far I've tried NN Smooth and Signature nic salts, Liquid Nicotine Wholesalers nic salts, and now trying Nicotine River nic salts. The NN Signature nic salts definitely has benzoic acid, I can smell it, and I think has a slight taste effect by it. The NN Smooth turned dark too quickly and as it did, the taste changed. The LNW I'm on the border with as if I like it, and so far I am liking the Nicotine River nic salts (no benzoic smell, I think they use a mix of cations/acids), but have only vaped one tank using it