It depends on how hot it is outside, but I usually open the windows for a couple minutes and then turn the AC on. The outside air, depending on the temperature differential, will cool the car to a certain point much more quickly than the AC. Typically the AC should be blowing nice cold air in about 30 seconds, and if it's blowing on you, you should feel it pretty quickly. I'd guess a good AC system will probably take something like 10-20 minutes to cool the average interior temperature from, say, 120 to 80 degrees. The thing is that there is a lot of material to cool, and while a good AC system will make you feel cool pretty quickly, it takes a lot more to truly cool the interior.
Tinting helps a lot, especially considering that a lot of the heat you really feel is from the sun shining on you. I'd guess that tinting probably reduces the amount of heat energy coming into the car by something like 30% depending on the amount of sun, glass area, interior color, etc.
As for performance at idle, usually the two main issues there are airflow and compressor size. With the system on my Fairlane, a parallel flow condenser, electric condenser fan, and a Sanden SD510 (10ci), it pulls down pretty well even at idle. I'm not sure what the typical size of the 123 and 126 compressors is, but if it's 8ci or more I'd think it would be plenty. Then again, I'm not sure how the flow of the York and R4 compares with a swashplate design like the Sandens, but I would guess it's not as good.

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Once and future king:
'64 Ford Fairlane w/approx 238,000 - looks rough, but amazingly reliable if you know how to look after it; I will soon begin work to totally restore and modernize it.
Family vehicles that I lay some claim to:
'78 300D w/approx 350,000 original, '62 Ford F100 4x4, '90 Ford E150 w/171,000 original