In the past 2 months, I used a carbide 2.5" paint scraper to remove the many layers of built up paint and the crappy blobs of texture from all vertical walls in my 1973 built POS.
This process left many divots where the texture pulled off the wall, but by using 2 coats of thinned mud, after sanding the wall was perfectly smooth. In addition, like yours, the tapped seams were terrible, but when I was finished they were nearly invisible.
IF you scrape your walls, you don't want to go through to the drywall surface, just knock off the high spots, so when you apply new mud, it goes on smoothly. Something that really helped me was thin mud and using a broad knife. When applying the second coat, spray the wall lightly with a mist of water after getting the mud relatively smooth. It's impressive how smooth the mud turns out, ultimately it needs just a touch from the sander. I found it easier to scrape and smooth with mud than applying new mud over the top with out scraping which took something like 4 coats. Don't know what your situation is...but I at the same time I scraped the acoustical texturing off the ceiling (glad that crap is gone!).
One wall in particular had many bubbles under the tape, and what I learned was the original tappers filed massive cracks with mud, which later on, pulled away from the tape. If you have to remove the tape, take a knife, cut along each edge of the tape, through the mud and paint. With a putty knife and a spray bottle, start at one end and lift the tap out of the joint. Spraying a small amount of water on the tape really helps it to let go of the mud. Repair the mud in the joint with a narrow knife (I used a putty knife) making sure to keep the edges of the channel relatively clean. Lay new tape back in the track with fresh mud, feather the edges you'll be good to finish like it was new. Again...if there's massive amounts of mud on the seam...the paint scraper works well to level out large bumps, surforms work well too.
When you get the walls like you want, grab the texture gun and get to work. Granted this is a lot of work and wouldn't wish it on anyone...but the house looks fresh and renewed, and I'm glad I did it.
Good luck...
Darwin