From what ive found (and im no expert) THC is best for pain and battles cancer and tumers ect. CBD is good for well being and nausea etc. Thye both work together as a medicine. There are like 1,000 cannabinoids that are active that we don't understand as well.
Most medicinal plants I think are thin leaf based (Sativa in the old terminology) and has a high. Broad leaf (indica) has a more stone effect.
Tolerance of everyday users builds up so how it effects someone in the fisrt two weeks is not how they will be effected a month in.
Please take everything I say with a grain of salt. im no expert and have been flying by the seat of my pants, but its information non the less.