You can have a Base Color texture be 1024x1024 while having its corresponding. When creating HD Textures, the best way to avoid this limit is to only utilize high resolution textures for textures that absolutely need the detail. We are working with Microsoft to alleviate this limit in a future update. The actual limit depends on the number and resolution of the textures, but as a rule of thumb, keeping the resource pack below 100 MB is a good idea.
What is the memory size limit of creating texture Resource Packs for Minecraft with RTX? And what are the best ways to avoid reaching this limit?