It’s difficult to tell how it helps during sessions as the effects are long term. It takes a few weeks for Creatine levels to return to normal after you stop taking it, so you can’t just stop for 1 session to see the difference. It does help gain muscle though, as I always weigh more after I stop taking it than I did before (after you subtract the difference from the water weight)
But despite the extra weight I don’t appear to be finding longer runs any more difficult than normal which is good!
Hard to tell what percentage is muscle/water/fat, but I am eating more than normal during this phase of my training to ensure my body is not short on energy/nutrients for muscle repair. When it is closer to outdoor season I will go back to my normal diet to make myself more lean for competitions and ensure I don’t have excess fat.