Poor AC while idling, great while on highway

I've noticed when air temps are over 90 degrees, my AC performance while idling isn't the greatest. But moving on the highway at 50+ mph, it seems to cool quite well.

The fan clutch has some resistance while spinning by hand (checked today after parked for 3 hours) but it's not significant. No play in/out of the fan blades.

After coming back from lunch, I parked it, left it running with the AC on and checked the fan. It was running but wasn't "loud". Coolant temp was showing 204 at the time (ultragauge reading). Shut the engine off and checked the fan rotation again- felt just the same as prior to lunch on a "cold" engine.

Unknown mileage on the fan clutch. 194,000 miles on the Expedition.

I'm thinking the fan clutch isn't strong enough to pull air in through the radiator while sitting still- but 50+ mph on the highway shoves plenty of air through it. What do you think?

Also, water pump? Should I change it at the same time?

And I forgot to mention:
Sometimes the fan will sound very loud. But only on occasional cold starts. The noise goes away after ~60 seconds.

Never hear the fan any other time than that.