Drywall Damage After Wallpaper Removal
I'm feeling lazy so I don't know how far I'll go in responding.
First off, is the wallpaper from the last two decades or is it older? You should try spraying the wall with water from a water bottle before you scrap. If the drywall was unsealed/unpainted before it was papered... I feel for you because that's a mess.
Once you have the paper removed, or all the paper that will come off after it's been wetted you'll have to make that call as to what you want. You've decided texture... if it's a heavy texture that will make thing easier (but I wouldn't do it).
Avoid sealing the drywall, don't do it yet. First go over the wall and remove all the loose gypsum and paper. Watch for bubbles, places where the surface paper is loose from the gypsum - cut these out. Next, pre-fill all the gouges... dent's... etc. with drywall filler, it's preferable to use a specialized filler but I want to keep this simple.
And to keep it simple... use mesh tape and tape over any places where the surface paper of the drywall is broken, cut, etc. Skim this tape with drywall compound. Let everything dry.
Next take a trowel or a wide knife... whatever works best for you and fill/smooth out the wall. Let it dry, sand and repeat until you are satisfied. If you think you have the knack... you should be able to skim the entire wall and fix as good as new ready for paint - smooth no texture.
If not, get it as good as you can, sand out any ridges, edges and as many imperfections as you can. At this stage you can prime/seal the wall then texture or texture then prime/seal... depending on the products you are using.
I recommend getting the wall as smooth as you can and then priming/sealing it. This way you'll see more flaws that you may want to fix, it will also help you find bubbles that you may have missed. These have to be gone before you can texture.
If you can't get the wall fairly smooth, you'll just have to apply a heavier texture.