I'm on 200mg of magnesium taurate. Magnesium l-threonate years ago when the hype for it started. Absolutely no difference in anything. Also taking l-theanine + apigenin (mix that Andrew Huberman recommends) - same effect. But for people with not-the-best diet magnesium is definitely beneficial for health so it's good to take it anyway.
Might it be a biochemistry thing rather than diet? I eat very few processed carbs and sugars and enjoy deep, restful sleep with most off-the shelf magnesium.
L-theanine is fantastic too with my morning coffee. Alertness without the jitters.