Hm, lots of good ideas here! For hunting I think hook studs give a cleaner look, though I don’t have a strong preference either way. Same with brass/silver.
For reins, I think you’ll find that preferences vary widely. I like rubber or rubber-lined reins. If I’m riding on a snaffle with just one rein, then I like them thicker, like 3/4 or 1 inch. But I have large hands for a woman. If I’m riding on a pelham with two reins, then I want a thinner rubber/rubber-lined rein on the snaffle ring and a thin plain leather rein on the curb ring.
In short, options are good especially for reins.
Oh, and built-in rein stops for running martingales are good. I hate having to attach the rubber ones to reins that don’t come with them. Even though I don’t always use a running martingale, I specifically look for reins with the stops just in case.