Varnishes, lacquers, polyurethanes are all clear coats, but they are not all the same. They all have different base chemicals and uses for different applications.
For a table, I would use lacquer. Lacquer come in several forms, water based, nitrocellulose, acrylic, and variations of each.
If you have already applied stain, I would then apply a Sanding sealer. You can use Dewaxed Shellac, Lacquer based, Polyurethane, or vinyl sealers for lacquer with great results. Then lightly sand it smooth with some high grit paper or steel wool analogs. Spray again, smooth again. Then start applying multiple coats of lacquer.
If you want a mirror finish, you can wet sand and buff the lacquer finish. Or you can just sand it lightly to have a nice satin finish. Or just leave it the hell alone. Just depends on what you like. In my opinion, lacquer is about the easiest and most beautiful finish to spray. It is very forgiving, and its easy to fix mistakes. Plus it cleans up easily with water or lacquer thinner depending on its base.