L/W, The first one is easy. Yes, I’m sure the glue line prevents the “creep” of solution below the surface. That means all you have to worry about is the surface itself. I mask carefully as shown and then try to “cut the edge” with my brush just as if the tape wasn’t there. It worked really well, this time. :-)
The second is a little harder. In areas that are difficult to finish, like the apron/leg area on these tables, I like to completely finish before glue-up. With hide glue the clean up is very easy and doesn’t bother the finish. In places like the top I know that I will have to scrape away some of the ebonizing and that will necessarily be the part next to the banding, so I may do it first to get a look at how it will look finished, (a color check) or I may just wait and do it all later. In this case it was one of each.
It is easy to re- ebonize if you sand or scrape through to bare wood as I did on the leg/apron transitions. It will blend perfectly.
The early bird gets the worm but its the second mouse that gets the cheese.