Unless the tracks require a controlled impedance choose a width that fits with the component footprints, just keep them all the same.
If it does require controlled impedance you are going to have fun on 2 and 4 layer boards as generally the requirement for bog standard digital is 50R, so for a 2 layer board 2.5mm wide traces and for a 4 layer about 0.9mm traces.
But as said unless there is a requirement for controlled impedance don't bother...