Compressed version requests: This is not a VN, this is a realtime 3D game, it does not consist of image sequences. So you can't compress realtime 3D games like VNs. Though you can downsize texture files, but game will look like shit and not worth the effort.
Better performance request: Only the dev can tweak the game for performance changes. Again this is a realtime 3D game, it can work on most PCs but not all PCs.
Most of the Vns are basically picture books with some scripts, that's why they can work on potato PCs without issues. Realtime 3D games uses/needs much much more CPU, RAM and GPU depending on the visual quality and quality of coding.