Basically it is a lot about basic graphic mapping file size and color depth.
Originally, 20 years ago, the game came with 512x512 8bit graphic files. Fancy for teh day, but quite crude and with lots of tiling when going closser. Today we are at 1024x1024 16bit as "standard" and 2048 and higher as "HD". That is a difference you see in color smoothness and texture detail on the ground and on aircraft. Of course, individual object modding with more detailed meshes and various effect modding went a long way as well.
To answer your question: Yes, BAT (and other modpacks) of course include such upgrades.
But for effects and other stuff there are wildly grown variants of mods which do similar improvements. Not all are compatible with one another, mind you. It's like a tree with many branches these days (or some say a jungle). But basically, with any more or less "up-to-date" modpack, you should be readily set up with a variety of improved graphics already.
Do the BAT or VP mod contain the graphics upgrades
As you see, there is no "
the graphic upgrade", as in definitive. It is just "One kind of" these days. If you fly on some map in BAT or VP, they both may be very upgraded from the "stock" version, yet still look different in some details.
GE (Graphics Extender) is something else, it's kind of constant beta and requires some additional fiddling and reading up on.