Changa 1:1 by far with caapi leaf and white freebase. I then eyeball some extracted caapi alkaloids (from white vine) and toss those in with the isopropyl, stir and evap in a small dish.
Changas much easier for me given im just using a chillum and a lighter. Trying to vape freebase on a bed of leaf is much more "hit or miss" vs throwing a small pinch of changa in the chillum..light the tip and drag it sllloowwww until i have a full capacity of vapor and then "full immersion into the Self."
To your bonus questions...if I had the GVG I would use changa all the way. (one day I will have the GVG.)