You should be using tapered edge plasterboards for taping & jointing. You’ll end up with a bump at every joint which will be exaggerated under certain lighting conditions. You should feather your joints out even further because of this. I suggest you visit YouTube for a few tips. Good luck.
Get your Mrs to hold an umbrella above your trowel as you plaster, or stop a few inches short and put a wallpaper border around. Seen some nice Buzz Lightyear ones in B&Q. (Borders, not umbrellas) Hope this helps.