I've on of those glass carafe's with the insert for coffee grounds, but I use my french press because it's just easier. I do 1:4 course ground coffee to water, so it's a concentrate. I use 200g coffee + 800ml water in my press. I let it brew in the fridge for at least 12 hours, up to 18. Can go to 24, but that's not my preference.

At serving time, I like it with generous 1/3 coffee concentrate + lean 2/3 water.

If I did not want to make a concentrate, but to drink straight up, then I'd go 1:8 or 1:10.

It's all about taste though! You'll find your sweet spot after a couple brews. Course ground coffee makes a much "cleaner" cold brew than regular grind. I don't generally filter mine unless its super cloudy.