Planning Ideas
Rick Steves İstanbul has good walking tours (will reference this below)
I’m sure other books have good walking tours, but I know Rick tends to hit the highlights and mention the interesting points pretty efficiently.
NYT 36 Hours on the asian side (2015)
This looks very interesting to do
NYT 36 Hours Istanbul (2007)
https://nymag.com/strategist/article/istanbul-turkey-itinerary-things-to-do.html