If you are only getting a cutout after using ReMask, you will need to go to your Preferences within ReMask in order to enable the layer mask functionality.
To do this, open ReMask and go to Menu-> Preferences.
Within your preferences, check "Enable Use-Layer-Mask".
You will then need to exit out of ReMask and re-enter for the changes to take effect. After returning back to your host editor, you should see the cutout on a layer mask.
To make changes to the layer mask, please make sure that the mask is selected in your layers panel (rather than the image). Press B to activate the brush and then X to toggle between black and white (white = keep, black = erase). You can then refine the mask as desired.
See here for more information on using layer masks with plugins if needed.