VST Performance

Hi All,
On the VST performance meter, what are the references of the 3 displays? In other words, what would it take to improve the performance of each?
I imagine they display the performance of the sound card, ram, SSD access and processor but what does which?

Average Load - On a medium/large sized project is about 33% but sometimes spikes when the sound card is set at 256 in the audio latency.
Real Time Peak - Is barely on the scale.
Disk - No discernible reading.

Thanks for your thoughts.