When I started DIY, I initially purchased 36mg nic for similar reasons - I was unfamiliar with it, afraid of a mess or spill on my hands. Then I mixed a few times and found a simple routine that worked for me and thought why wouldn't I buy 100mg - price was the same as 36mg and it took up less space in the freezer. I mix by weight so the math (and mixing) is easy. No kids, but I am careful around the cat. I think she likes juice, she always watches me..LOL.
PG is a lot thinner than VG, so it's easier to pour and mix. My easy recommendation, if you like high VG, get it in VG base because flavors are usually in PG, if you like high PG, get it in PG because then you're not adding a lot of VG. If you are in the middle, they both work and I might go VG because you'll be adding more PG to dilute it. I have some nic in PG and some in VG. They both work and that's all that matters to me. There are some discussions as to which last longer in a deep freeze, some lean towards VG but the difference is probably nominal if stored properly.