A single serving method (from James Hoffman YT channel) I use is:
16g coffee
150g water
100g ice
I make the hot coffee using the above 16g coffee and 150g water. My brew time is four minutes. Then, I pour that hot coffee over the ice and stir until the ice cubes are melted.
Cold brew shaken with lots of ice (and if you are me, some simple syrup). Cold brew is strong and smooth, and using more ice in shaker lowers the temp fast so less dilution. Strain over more ice in insulated cup.