The temperature reading is within a few degrees no matter where you put the sender so it doesn't make to much of a difference. The reading in the pan does respond a little faster to changes but again it really doesn't matter. I like to Put it in the pressure test port (which is 1/8" NPT) because it's way easier and to keep the wire out of the reach of exhaust and to keep it away from be being snagged on bushes etc.
Your operating temperature should be no more than 90 degrees higher than ambient air temp, i.e. 70 degree day = 160 degree fluid temp. If your trans runs consistently higher then you don't have enough cooler capacity. There will be times when the fluid could get 230 or higher such as slow speed hill climbs or long grades when the converter unlocks this is normal just make sure it doesn't stay that hot for longer than a few minutes and shut it down at 250 degrees