What should the air temp coming from the AC vent be?

Hello reddit.

Maybe this has been answered before, but all what I could find were answers like (the air coming out should be ~20 degrees less than air coming in). I don't really understand this by simply taking an example.

Air in TX/AZ other hot states can be 110+ degrees. So the air coming out from the vent into the house will be 90 degrees??? It's somewhat difficult to image this being right.

I have a brand new system SEER14, 3.5 ton unit (I'm in midwest). The air outside is 85 degree. I turn the system on, the air temperature coming from the vent is ~55 degrees, which is fine - it gets the job done. But I measured the air temp coming from my relative's house - theirs is 45 degrees cold with a 20yo unit (same size house/unit).

Is there something wrong with my brand new unit, or it works the way it should I and expect magic from a brand new unit?