I always remove the paper before I sew blocks together. I draw a .25" seam line on the block to give me something to follow and pin when I need to. Just think about the size of even a twin or lap size quilt. I don't want to remove all that paper t one time. I would be a nightmare.
PP has a lot of bias edges and I starch the fabric back before I cut it to work with and I starch a second time on the back after I take the paper off, before I sew the blocks together. It just gives me more control.
You can also only remove part of the paper to sew the seam but I find this to be twice as much work.
One other thing I do sometimes is to do a basting stitch first, just on the outside of the .25" seam. Open the blocks to see if the seam is good and then do the actual seam. This helps greatly in getting accurate piecing.
As an aside, there is a phrase that is used all the time referring to accurate seams. I really don't care about the seam as much as how the block finishes. So sometimes there may be a narrow seam to compensate for a bad triangle edge or something. It doesn't matter as long as the blocks look good after they are sewn together. And yes, in a perfect world our seams would all be that scant .25", but who live there!
Happy PP.
peace