My thoughts are that the Commandment Laws are comparable to the Sins' Sacred Treasures, so when the Commandments get their powers back, their abilities will be able to be used in conjunction with their Laws.
As for the powers themselves, I'm unsure. It could be a number of different things. Powers are pretty varied in Nanatsu no Taizai. Monspiet's technique, given it's name, seems to just be a variation of the Hellblaze enchantment that Mel and Hendrickson used, not his own unique power. I could be wrong though.
Average level of power is probably varied as well. They'll all definitely be over 30,000 at the least.