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.

raphma