Just some thoughts... at least one nic vendor suggests that long term storage in VG is somewhat better, but I've seen some controversy over that.
The bottles of nic I bought from MFS say "SHAKE WELL BEFORE USING". Ever tried shaking up pure VG? And it seems to me that, as DIYers, the most likely problem we might have is a "layered mix" where the nic we decant for a particular batch may not be the average strength. Consider that your source of the 100mg concentrate probably mixed 1000mg pure concentrate in with the PG/VG base. In a totally worst case scenario, they might have just squirted the pure nic into the bottle, capped it and shipped it. I am not suggesting any nic vendors do that, I am just being philosophical with a worst case scenario, and I think it would be prudent to assume that is what was done???? Just to be ultra-conservative and to be masters of our own destiny. Leave nothing to chance.
From that point of view, it would probably be safer to get a PG only base, simply for ease of initial mixing. I personally have bought 3 bottles from MFS in 50/50, but if I ever need more I might go PG just for this reason. You may also want to consider pouring the entire bottle of 100mg nic into a much larger bottle to shake it up before splitting into smaller bottles or decanting the top off for your first batch. The bottles, as shipped, are usually filled as full as possible to minimize oxidation but that does not make it possible to mix properly. I used an empty and well rinsed 2 liter pepsi bottle.
You may also want to buy a basic nic test kit, such as what Wizard Labs sells. Then you can test what you decant for a mix, and/or test your final base mix to make sure it is within reason. I bought the Methyl Blue and HCL from WL and found that my MFS tested within 10% of the labelled concentration, or my final mix, and that is as accurate as I can probably do since I am a bit color blind. And that was from an earlier buy that I never shook up properly before decanting off into some smaller bottles (my bad, but I am still learning!).
You also need to consider your final PG/VG ratios. If you like super high VG concentrations you may want as little PG as possible, and then you might want a 50/50 mix, or even hassle with shaking up pure VG.
ETA: in your case, since you like 50% or greater PG mixes, then buying in pure PG base would not be an issue in terms of getting the final mixes you want. My note was more for others that might want to avoid PG to the extent possible.