Those mods you mentioned wont use much vram.Only texture mods like Skyrim HD 2k or SMIM will fill your vram.So if you plan to use only lightning and script based mods 2GB is more than enough.
BTW i dont know your specs but since you mentioned Realvision know that ENB mods can cripple your performance.
Im using the official HD pack,Improved NPC Clothing,SMIM,Vivid landscapes,Improved Ruins Clutter,The beauty of Skyrim caves dungeons and mines,a couple of hd hair mods and i dont use more than 1.3-1.5 GB.