I’m on record as saying I love the Slow advancement track for Pathfinder. I was recently asked for my advice on how to convert an adventure path to the slow advancement track. While I ponder that, I thought you might be interested in these slow advancement track resources:
Pathfinder: The Slow Advancement Track
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Creighton
Creighton is the publisher at Raging Swan Press and the designer of the award winning adventure Madness at Gardmore Abbey. He has designed many critically acclaimed modules such as Retribution and Shadowed Keep on the Borderlands and worked with Wizards of the Coast, Paizo, Expeditious Retreat Press, Rite Publishing and Kobold Press. View all posts by Creighton
I think 5e got it right. Characters level fast at first so they’re not totally useless then leveling comes to a slow crawl.