I buy from nicotine river (nic salts) and heartland vapes (their budget nic). I find both of them to be fine, but I was using nic salts at first because my respiratory system was pretty torn up when I got here and nic salts are (usually) smoother.
I would consider maybe trying different vendors in small amounts to see what you like best, if you wind up with any preference at all, I mean some people just aren't crazy sensitive to nic differences, etc.
I started with 48 mg./ml nic (I was worried, I can be clumsy) but quickly moved to 100 mg/ml due to space reasons and the fact that I was having no issues whatsoever. I actually don't use gloves for my nic, because if I get some on me I want to feel it so I can wash my hands, not spread a thin film of nic everywhere honestly so no gloves for me.
When I was not using a premixed base of all ingredients but flavors at the correct nic strength (you kind of have to know what your "general standard flavoring base" is though for that, to a fairly reasonable degree, I flavor usually around 10% so I just factor that in to my calculations and have ready mixed base, makes thing so much faster) but I would do the nic first, take care of any dribbles or spills, and then just deal with the other ingredients hence minimizing my nic exposure.
Although unless you are using some ungodly high percentage of nic (which you should absolutely NOT do) well, even if you have some catastrophic spill,, you're gonna have time to get to the shower and wash it off, nic is not instantaneously absorbed through the skin, so you know, use due caution, but you don't need hazmat procedures or anything.
Finally, go with PG base if you can. I am PG sensitive so I have to use 100% VG base and it is gloopy, it's harder to handle, it's a pain in the rear, etc.
Good luck and happy mixing!
Anna