For plinking, muzzle flash isn't an issue. I get it when using Power Pistol powder. You're not going to hurt anything.
My favorite powders are HP38/Win231. It meters like a dream, fills the case fairly well, and lowers felt recoil.
I see you're using plated bullets. BE SURE to use charge data for cast bullets. If not available, 10% less charge weight from the published number of jacketed bullets you're wanting to use is a good rule of thumb.