What is the max supply of Ethereum?
there is no max supply for ETH.
What is the max supply of Monero?
there is no max supply for XMR.
Is there a all in one wallet that can store all these altcoins? If so which is the best wallet to use?
i never used a multi currency wallet, so i don't have a personal opinion on that. but i think jaxx.io have them all.