FWIW every study I have read stated that creatine supplement was no use for most endurance athletes. There was one notable exception: vegetarians ( guessing you read the same memo). As I am one, I took it. The impact took 3 to 4 weeks to manifest for me and was mild at first. There was a marked increase in strength endurance not strength or power. I could just keep on keeping on. This was without specifically training for that. At the time I was just aimlessly riding. So I am fairly sure that the effect was real. I am almost pure ectomorph. More meat on a butchers pencil.
Your symptoms sound to me more like hydration issues. If it is causing water retention then your electrolytes are going to be out of whack. Which would come into play more at threshold. Also the cramps are a fairly big red flag. Maybe start dropping some of them electrolyebtabs and magnesium.