For cold coffee i either do cold water in the French press and leave it in the fridge or "Japanese iced pour over" using a v60 (think there's a Hoffman video for it). Wouldn't bother buying a dedicated device for cold coffee unless one or other of the above methods weren't working and even then if you have a v60 or similar you can just dump coffee in a big jam jar and filter it the next day. I do have the mizudashi but it's just because I like to support my local coffee man
For cold coffee i either do cold water in the French press and leave it in the fridge or "Japanese iced pour over" using a v60 (think there's a Hoffman video for it). Wouldn't bother buying a dedicated device for cold coffee unless one or other of the above methods weren't working and even then if you have a v60 or similar you can just dump coffee in a big jam jar and filter it the next day. I do have the mizudashi but it's just because I like to support my local coffee man