They make a mudable J bead.............Or L bead
Trying to understand, tile is staying and you are butting new drywall up to it? Will it be flush or set back?
If the drywall is finished set back 3/8'' or so there is no point in using anything. Cut the rock tight and either grout or caulk.
The plastic j trim is only paintable, you can mud the metal :thumbup: