I plan on consuming Bolivian torch cactus green flesh powder in capsules tomorrow. I'm well versed with lsd,lsa,weed,dmt,dxm,4-ho-mipt,amanita,salvia,bufotenine,ecstasy,nitrous, and harmalas. My main concern is being underwhelmed but I'd prefer not to be overwhelmed as well. What dosage in grams would you recommend? I am considering 20-40g. I weigh about 120lbs.

I think you're about right. I feel pretty nice achuma at 5 grams like a threshold, I think you'll do right with 20.
Then I only use these outer skin powder for low or microdose.

It would not be bad to assume 1%, then 40g would be 400mg, that's a good dose for a person who weighs 120lbs. If the material is 2% 800mg is strong but shouldn't be out of control.
It's improbable that it is stronger than 2%.