The most straightforward / brute force way to reduce VRAM usage would be:
bulk-edit your imported textures and increase the LOD bias.
The question is, whether in the editor itself you’d get the full memory benefits… it’s a bit unclear according to this very old post: Need confirmation on LOD bias for textures
Another thing to consider is, are you actually getting lower framerate when the VRAM is slightly over-used? I’m perpetually in the same situation and somehow it doesn’t actually seem to affect my framerate in the editor?