I had the same problem. Here’s what helped me: First off, PIE(Play In Editor) automatically adjusts scalability settings to keep performance up. This was unknown to me, and is critical to understand. And you can turn it off!
Settings>Engine Scalability Settings>Monitor Editor Performance
You will see much closer framerates to what the build was showing (There wasn’t any way for me to mirror the performance of my editor to the performance of my build until this was turned off.)
With that turned off your profiling from PIE will be much more accurate so you can optimize your lights, foliage, and any other performance heavy things.