How easy is it to make your own ejuice and does the vg/pg mix really matter? I get the impression the higher the vg the cloudier the exhale.
Welcome callumari! Yes, DIY is relatively easy. The link to the DIY thread is perfect. Read blogs by Hoosier, Dannyv45, and Bill's Magic Vapor. Each of these guys is incredibly experienced in juice-making.
PG/VG does make a difference. PG is thinner and provides more "throat hit". VG is thicker and helps yield more vapor. A lot depends on the type of topper you're using as to whether you may have success with one PG/VG ratio over another.
They all have recommendations of gear to get and types of flavors to have in your arsenal. There are a decent number of flavoring bases - Capella, LorAnn, FlavourArt, The Flavor Apprentice (TFA) among many. You may find that you can make all your flavors from one manufacturer; you may have to have bits and pieces from many. Just depends on what you like.
The same flavor from different manufacturers probably will need different percentages. Example, you might have a Vanilla Custard flavoring from Capella, and it calls for one percentage in a recipe, but if you have a Vanilla Custard from TFA, you might need a different percentage to yield the same flavor.
Start with small batches. You don't want to jump into a 60mL bottle, only to find it's disgusting
Bill's Magic Vapor talks a lot about 100DT - 100 Drop Test. Basically, you count the number of each drop of each flavoring (which constitutes 1% of the overall mix) and then fill the rest with enough PG/VG and Nic to make the balance of 100 drops. You can let it sit for a time (steep, if you will) or try it right away (ATM - at time of mixing). You should get about 3-5mL juice, depending on the size of your drops.
Take GREAT notes, or else you'll come up with a fantastic juice that you'll never be able to properly replicate....
Good Luck!