I've been experimenting with Rebol on Try It Online! recently using this tutorial, and have been enjoying it so far.
I want to code locally on my machine with Rebol, on VScode, but there only seems to be a plugin for Red. Is there any large difference between Rebol and Red, or can I just download that and start programming using it?
Speaking on a high-level, Red doesn't add much to the "language" itself. It can compile some constructs, but the more interesting interpreted constructs it can't compile (so it embeds an interpreter in the compiled executable). For learning, this just adds a speedbump...there are bugs that are in the interpreter but not the compiler, etc.
At this juncture, I'd suggest using a Rebol2/View interpreter, for friendliness:
If you just want syntax highlighting, the Red highlighting should be basically the same.
But hopefully soon after getting comfortable with the basics you'd be interested in working with (and hacking on) Ren-C. It's where all the language acrobatics are.