I am a 1% guy, always comfortable with that amount. Whatever you play, it must be low enough so that you are comfortable, but high enough so that you aren't tempted to fire away on games where your opinion is marginal. As for 5% or 10% plays, I suppose that could work for some, but I'd hate to drop 30% of my roll because I lost 3 straight!
Many factors to determine success. Size of BR, % of BR/play, number of plays per day/week/year, win%, ROI, juice, bonus. Many ways to skin the cat, not one size fits all. Unfortunately many, many more ways to fail. Steepness of the learning curve and ability to survive it also dependent on several choices/factors. I wasn't the fastest learner, but I was determined to win long term. I wish I would have made some different choices along the way, but I'm thankful that I was hard headed enough to persevere through the losing times.
Keep an open mind towards anything that may improve your bottom line and think long term. In the end, that's all that matters.