What about position sizing? What is the maximum amount of contracts I can trade?

Every account size has an allowed number of contracts that you can trade simultaneously, therefore if you have a 50k account the maximum number of contracts will be 6, you can execute a position with 2 contracts on NQ and at the same time a position with 4 contracts in the ES; you can have a position with 6 contracts as well. In any of the instruments available.

25K Account	3 contracts
50K Account	6 contracts
100K Account	12 contracts

The commission per every contract is 5 USD (round trip)

Note: In the instruments E-Micro are available the same number of contracts, the commissions for these instruments is 1 USD (round trip).