So I’ve seen a couple mods that have their YDDs in one rpf and the YTDs in a completely different rpf and I am basically wonder how that’s done, I am trying to make a small pack and I’d prefer to have the textures located in a different rpf if possible.
If you're trying to make a small pack, having 1 rpf might take up slightly less size, less overhead, than multiple rpfs.
Examine your mod example which has its textures separate from its drawable to see how it is configured. For example if this is an MLO, see how they structured the files and folders, particularly content.xml and setup2.xml. In other words use those mods to guide you and ensure the paths are properly implemented.
I’d prefer to have the textures located in a different rpf if possible.
Adding to what @JohnFromGWN said. Yeah, that's totally possible .
Basically, as long as the '.ytd' & '.ydd' are set up correctly, the game/'.ydd' will find the textures wherever you place them in the game. All that's really needed is that they are named correctly & are loaded by the game, the game will do the rest & find them & apply them automatically etc.
Follow @JohnFromGWN's advice & copy something pre-existing. The easiest way to do that is often to download a mod that does similar & adapt that to your needs. Much easier than trawling through 1000's of vanilla files to figure it out etc.