Our Bathroom was wall papered, which we took off using fabric softener and pelling it away. There is now the glue/mastic stuff here and there on the wall. How important is it to remove all of it if we are going to paint it with textured paint? (I believe we will be putting the texture beads in the primer-unless someone here tells me differently.

I suggest you get everything off the wall before you start a project that big. You want it to look perfect, so start with a good surface.

I was hoping to avoid scaping it all off, it is patchy but a thin layer. Any other experts think I can avoid what Tickle is suggesting?

I agree with tickle, best to start with a good flat surface. The problem with not removing it is it may come up when you are painting and look odd. It shouldn't be that hard to remove, just spray it down with warm water and wall paper remover (DIF), let it soak in good then it should scrap off with t mud knife. Wipe it down with a sponge after. As far as your texture, there are many methods and textures that can be used. Not sure about the beads in primer method you mention.