The short story is that dual-device wearing has some perks but may not be for everyone.
Buy the Galaxy Ring and Watch together if charging schedules give you anxiety, or if you frequently go from sweat sessions to formal affairs and need a subtle tracker as often as you need a dedicated workout tool.
Don’t buy the Galaxy Ring and Watch if you’re comfortable tracking Zs in the latter, your priority is detailed wellness stats, and your go-to workouts include weights, bars, and handled exercise machines.