@ Kathy
In regards to P3 please see this support forum thread which includes comments from the plugin developer about its accuracy. I suggest looking at using the Query Monitor plugin. You’ll notice on non-Connections pages, the impact from Connections is next to none. On a Connections Page you will see an increase in database queries, those are necessary and only affect the page load time which the [connections] shortcode exists.
If you want to really did deep in monitoring your sites performance, I recommend New Relic, W3TC has built in integration for it. If you’re on a shared host, it will be unlikely that you’ll be able to use New Relic. I’ve only recently installed this myself and still working to understand all the data it captures.
I hope that helps.
