In general I agree with leeneia. I've been doing all those things about as long and the mode has never made any difference to what got played or how. While actually playing music it just isn't important that "Old Joe Clark" is mixolydian and "Douce Dame Jolie" is dorian. You just learn the song.

I did sort of find a use for knowing modes recently. I said, "Let's do a G dorian jam" and just started to play without having to offer any further explanation.