Within GASE4 I’m not sure if each pad has its own insert fx, but a workaround is to activate the multi-outs and use inserts from within Cubase. I don’t think GASE4 is a standalone product so it’d probably make more sense to add insert fx to your Cubase mixer.
In the arrange window, when I cut and manipulate a segment of audio I get the option to create new version. I think this is what you’re looking for. So the snippet of audio you slice needs to be saved as a new version. I won’t have C7.5 until Friday. Hope that points you into the right direction.