I'm glad to hear that you're enjoying the Peak. Dunno if the 105 will be a step down, or merely a lateral step, but having more than one airbrush does give one some insurance when things go awry.
That's why I have so many of the same series, my Badger 100LG, 150 and 200-20 all share air valves, head assemblies, and washers, and only the needles can't be shared between the 100/150 and 200. Actually, I could use the 200 needle in the 100, it would just stick out the back end. The 100 needle is too short to use in the 200.
I've never provided instructions that say to use petroleum jelly? I
always recommend glycerin! Anyway, Vaseline is a brand name of
petroleum jelly, so other brands should work fine. Though I don't think I
would use it if I didn't
clean and lube my needle each time as petroleum jelly can collect
contaminants over time. But since PJ and Glycerin are interchangeable as (ahem) personal lubricants, they would be both effective for your airbrush.