Does the contract size vary for each Cryptocurrency pair?
Yes, it varies. You can check the contract size by the following steps.
Open MT4/MT5.
In Market Watch window, right click, open "Symbol" window
Select a currency pair - Go to "Properties"
OR
Open MT4/MT5.
Press Ctrl +U
Select a currency pair - Go to "Properties"
You can also visit Cryptocurrencies for details on contract size.