Hi,
Your answer is exactly correct. The lock contention is depends on INITRANS & PCTFREE .
The first is no of transactions can update that datablock simultaneously is depends on INITRANS.
The second one is if u set INITRANS to more than 1, it allows two TX's can update on that datablock. then the contention is switched to the available space, to update the row(s). If u have not enough space to update the row(s), it causes the TX to wait. The space available for update is defined by PCTFREE.
Other parameters are not related.