thanks so much for the info!
You are welcome and a belated welcome to the forums.
You are probably getting the best compromise in performance Vs protection. There are many people who previously reported 10-15 second start-ups with firefox, so 3 seconds is excellent and if you have a slight hit because of scanning/protection, it is still much better than most are getting.
When I start my computer, I start my email program and my browser and a couple of other programs and they are on all day so an extra couple of seconds to load over the day is negligible, especially when you consider how long you wait for windows to start.