Not sure about the others, but I've tried capsaicin and it's not the same. I got more of a gradual burn with the cap, even MTL'ing it, more akin to what you get DL'ing 6mg. Not for me. No substitute for the punch of a good, clean nic.
I don't like vaping stuff with more than 70% VG either, PG is essential for me as it accentuates the sting from the nic.
Sometimes I wonder if this isn't something that's being at least partly engineered by vendors from within the community. When you consider that nicotine is by far the most expensive component in juice, coupled with the fact that DL'ing high-VG (which can easily be obtained in bulk for fractions of pennies per ml) at high power leads to massively increased product consumption... Well, let's just say that I'm sure juice manufacturers love to sell those big bottles of 3mg 100% VG stuff. Ya think?
/tinfoil hat