There seems to be a bug on the current 4.14 Editor Memory Leak, to reproduce it you just need to start simulate game on and then toggle Possess/Unpossess or Stop/Start Simulation. I rise from 2 GB target to 9 GB in 30 seconds of doing this. It seems to take longer to Unpossess/Possess also.
Had both Project Settings and Editor Settings open whilst PIE, both had impact on memory release if done repeated times, Project Settings had way more impact ( roughly 1GB per PIE). This solves it, thanks.