Can you elaborate on your experimentation processes Haps and how you have come the methods described?
I have heard of preheating cannabis in an oven but have not tried it. I do not see a real need, the cannabis will be heated and agitated in solution for 30 mins to 3 hours anyway, baking for X time doesn't seem truly necessary.
It would seem personally that 325 degrees is too much and that smell is the result of cannabinoids like THC boiling off, as THC boils at 314 degrees F
That would imply to me that one would not want to preheat cannabis above perhaps 310 degrees F.
Thinking further though it may be a good idea to decarboxylate THC before making butter, but this depends on whether decarboxylation occurs while cooking butter, which I believe it does. Though it may be that pre-baking may be better as THC is already decarboxylated before adhering to lipids and the process will run faster, THC not having to decarboxylate in solution before adhering to lipid.
Re the vegan Q - I've read that saturated fat is preferable for extraction because it's more readily digestible. Coconut oil is highly saturated - give it a whirl.
I did a test once with clarified butter, coconut oil & olive oil - same amounts of everything, same cooking technique, etc. The butter & the coconut oil were both more potent than the olive oil ...
I've used a crockpot and didnt care for the results as much as on the stove. IMO the low setting on my slow cooker was a bit too hot. I like to keep the temp where it will simmer but take a few minutes after stirring to simmer again. I keep that process going for hours. Simmer, stir, simmer, stir..etc.. definately do not want boiling, just a few bubbles around the edge.