I was also having the problem where memory usage went through the roof. I tried the old UI change but that didn't help.
I noticed that it was the processes that were in the background that were using all the memory so I tabbed to one that had high usage and the memory usage went down for that process.
I then turned off the frame limiter and the problem went away!
My frame limiter settings were "Enable frame limiting when in background" checked and "Render game scene" unchecked.
I'm going to experiment with enabling with a low FPS but thought I'd post my initial findings in case it helps someone else.
Edit:
I've done some playing around and found that I can enable the frame limiter but I need to set it to render the game scene and have the target fps set to at least 1. Over time, the process memory usage dropped down to just over 300mb.
Note that I play on the test server. Here are the settings that work for me..
