Hi, could anyone advice what the NetSuite system in the APM breakdown consists of? There are barely any workflows so I'm sure it's not that

Includes server time, scripts, and workflows which I think is a bit misleading. I confirmed this in my sandbox and with NetSuite support. I am not sure how they specify out some of the script time but not all of it. I am guessing things like query, load/save that happen in a workflow are all considered server time. If you have a SB you can go to scripted record and just disable all of them to see the difference or one by one to potentially tack down the trouble maker.