Ideally each butted end or corner would be tapered, if using the joint tape method, but this is not always possible and you can get away with them being square, and the thin coat angle beads are applied to the external corner.
I personally prefer the self adhesive nylon tape rather than using paper tape to joint internal corners or butted ends, as it will help prevent dry spots and bubbling.
It would be common to apply joint taping compound to tapes and on first application to bead, apply joint filler before applying joint compound, but you could use joint compound only, it may take a couple more applications of this to bring the finish to being level and smooth.
The applications of these compounds and fillers require dying times and sanding and second or third applications, sanding after each, until you have reached the desired finish. They would then require priming prior to paint being applied. it can be quite a time consuming process and small areas can be costly with regards to material costs. I would personally skim it, if you have the skill!
