I try to keep things simple, so this is what I do:

I make a concentrate of 500ml distilled water with 25g espom salt and 12.9g of baking soda (sodium bicarbonate). Then I add 3.5gr of that solution per 1 Liter of water. So far it is not bad I see some positive changes compared to TWW water, somehow it just did not work for me. I drink mostly medium-light coffees pulled 1:1.9 to 1:2.5.

Is there anything you would add or change to the recipe in your experience?

That's a reasonable recipe, comes out to 71 mg/L hardness and 54 mg/L alkalinity in CaCO3 equivalents. The sulfate ion is 68 mg/L. Compared to TWW you have higher alkalinity, lower hardness, and lower sulfate.

You might want to experiment with less Epsom, maybe even down to zero to see if you prefer the taste.

Yours has about 25 mg/L sodium, which should be fine. But some people think that even that small amount might be enough to affect the taste, and use potassium bicarbonate in place of the sodium bicarbonate. Potassium is heavier, so In your recipe you would use 15.4 g of potassium bicarb in place of the 12.9 g sodium bicarb to get the same alkalinity.