You may need a lot more power than 300mW to cut white paper or aluminum foil. Regarding spectrum for the best burning, most people here recommend 445nm due to the $$$ per mW. If someone who actually owns violet and blue lasers says otherwise, then ignore whatever I said.
Anyway, sorry I cant give you the exact answer you need, I am still shopping for high powered lasers myself.
Hope this helps somewhat. :yh: