Absolute drawdown - this is the overal amount of drawdown. If for example I had 100,000 dollar account and I went down to 90k, my absolute drawdown would be 10%. This is based on no other trades into the story such as prehaps I had a 5% winner previously and then lost 15k in my second trade.
My relative drawdown will be considering the 5% trade winner I had and therefore say I had a 7% Loss after a 5% win. The drawdown in relative to the amount that was in the account which was 105k, not 100k. It is relative to the current level of profit or loss.
There is something also to consider, is that if you have trades that are live and negative, this will add to your drawdown. This can be a reason why you may fail a prop firm challenge.
Maximal drawdown I have no idea about but hopefully this is a partial answer for you.
Crash101