in my first project i have used 0,75mm for the data cable and 2,5mm for the 5V and GND cables.
I personally found it hard to solder the 2,5mm cables as they are thick for those small led soldering points.
Did you also already used 2,5 mm cables and have problems with soldering?
Or did you solder a thinner cable and then connect it to the 2,5 mm?
If yes does this work without having voltage drop?