Grace Ice and Water Shield.

https://www.lowes.com/pd/Grace-Construction-Products-36-in-x-36-ft-100-sq-ft-Rubber-Roof-Underlayment/3064819?cm_mmc=shp--c--prd--bdm--ggl--LIA_BDM_103_Roofing-Gutters--3064819--0--0-_-0&ds_rl=1286981&gclid=Cj0KCQjwiNSLBhCPARIsAKNS4_fuYgpE5RbgWh0zDrBrCG-KsDKEtT2EkLyjWoMAg7n0aLVWUTjhoCYaAi4AEALw_wcB&gclsrc=aw.ds

Umm.. not sure what you mean by that ᾑ4

I'd never heard of peel & stick removable wallpaper, so I did a search. The ones I found said to only install it on a smooth surface. You could buy a roll and try a little on the wall as it is to see whether it will stick sufficiently and not show the texture from beneath. I can only guess the texture from your one photo, but, if it came to smoothing the wall, I'd be more likely to do a skim coat of mud and repaint it, than I would be to sand what's there.

All wallpaper needs a fairly smooth wall, for the wallpaper to fully adhere to the wall, whether its peel and stick, or regular type wallpaper. Your surface is not ideal for wallpaper. You could sand it all down, etc, but, then the wall is ruined unless someone pays to get it redone, after wallpaper removal. Even if you can get it to stick, you will see every one of those texture bumps on the wall, on the surface of the wallpaper, and it wont be a good look. And the look of your seams, over a bumpy wall, will not be a good look.