Apart from obvious bitcoin which established altcoin is the best overall backed up by good reviews?

Bitcoin has a max supply of 21 million coins,

What is the max supply of Ethereum?

What is the max supply of Dash?

What is the max supply of Monero?

Is there a all in one wallet that can store all these altcoins? If so which is the best wallet to use?

Im from UK and like to know which is the best exchange for me with the most volume for altcoins like these?

Thanks,