How do I renovate these walls to be smooth?
I have removed similar wallpaper multiple times and if it is like the type I have removed it is actually relatively easy to take off of the wall.    You will simply soak it with a hot water and vinegar combo over and over until it peels off easily.   You may need to soak one area 4-5 times over the course of an hour but you can do everything at the same time so a room should be about 2 hours.
However it leaves behind tons of gook, paper and glue on the walls so you will have to let it fully dry and scrape and sand basically the entire wall.
The trim will pop off.   After that though - depending at what point it was installed and how it was installed - this could be little to no work or a lot of work.   If it were installed on a finished wall it will be a tiny bit of joint compound and sanding.    If it was used to conceal a &quot;gap&quot; for the cove it will be a ton of joint compound and sanding.   Still doable for a novice and really the biggest issue is everything needs to be covered/removed from room when sanding.   The other alternative to the trim is install a more modern trim and it could look nice.
The cove corner....  Whoaaa.   Not worth it at all.   It looks nice in your picture and for you to spend days of work trying to get a 90 degree angle.   Well whatever you think it is worth but if I were renoing a house I would never for one second think about redoing those ceilings.   They look great - it is the trim and wall paper that make it look &quot;old&quot;.