How much do they have under management or their daily volume, etc?
Billions.
Billions for both or just volume? Money in accounts would be interesting as that's where regulators (or the FBI) will step in at some point if it looks like potential fraud.
No one releases money in accounts numbers.
Kraken was doing $711M in daily volume before the maintenance. [1]
Only the top 8 exchanges have cracked a billion in daily volume. [2]