Hello,
Did you make sure that the hardware acceleration works on your computer? If booting the control takes more than one minute, you have to check the hardware acceleration via the i-icon beside the drop down in the extended settings of the control.
It is not (yet) intended to change anything on the RAM via the user interface. Currently you can only do this with QEMU knowledge in a manually edited batch file.
Starting a virtual control in ctrlX WORKS creates always a batch file in the following path '%ProgramData%\Rexroth\ctrlX WORKS\virtual-controls\images\1.10.2\5fgvp1xv.user.qcow2.tap.start.bat'
You can create a copy of this file and edit the ram and cores there (-smp 4 -m 1G) means 4 cores and 1G ram.
Regards