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 https://titanfx.com/trade-crypto for details on contract size.