What are the chances I damaged my engine?

My car has been running strong. It still does. In the mornings it would sort-of bog after I had driven a mile or so for a little while. Then it would run great later in the day. I was trying to figure out what would cause this. I thought of "intake icing" I knew I had a leak in the radiator and figured 2/3 of the way full was low but would probably be okay since my engine temp gauge was reading dead center. Maybe it wasn't full enough to get to the intake to warm it it up. I got looking at things trying to figure it out when I noticed that the coolant level in the radiator when cold was about level with the middle or upper 2/3 of the water pump. I removed the water temp sending unit and put a pencil in to see where the coolant was. It was about 4 inches down from the top. I only did emissions like that ( I drove it pretty hard that day for 45min) and then 4 separate 20min commutes. It has been parked since waiting for a new radiator. It still runs and startd good.

My question before I put a new radiator in and fill with new coolant is.. From your experience what are the chances I have damaged something or warped the heads in that ammount of time? Mid 90 degree days temp gauge was always reading dead center. How much will reading change without coolant touching it?

Would I have noticed a performance change if something were damaged?