You can change the line up - i find you need to select the correct format for the match on offer. For example i have created a T10 comp and i have to change the lineups in Other - because the format is T10 the Test, ODI and T20 line ups cannot be changed as you haven't select to play in either of those matches. Again i havent tried playing a T20 Test or ODI in casual as of yet so havent been able to compare. But i have definitely been able to change the lineup, however i do have to change the lineup for each game as i notice the other line up defaults to the test lineup (this was for national teams)