I run several pages on my Garmin three fields on each. More than that and they are difficult for me to read. The top display on every page is HR. I try to keep it at 135-145 on the flatter sections, and average 16-17 mph. On hills I run it up to 150-160.

I am old and have a history that dictates that I pay closer attention to HR than anything else. I often have speed displayed, but find I actually go a little faster when I am not watching speed, focusing rather on breathing, HR and the mental part..