How far should home A/C be from the setpoint?

Depends how long it’s been sitting on, can’t really answer your question

AC should be at setpoint or 1deg off if its been running awhile.

anything else means something is wrong imo

Should only cool to about 20-25 degrees less than the outside temp. Anything more than this means your unit is oversized and will short cycle most of the year.

The difference between set point and actual temperature is really irrelevant. The industry norm is going to be 25 degrees less than outside temperature as someone already stated. But there are many variables in homes. If the house feels comfortable your thermostat could just need to be recalibrated.

You need Freon

Do you live in a newer home? Or do you live in an older one with lapped siding, single pane windows and insulation older than the last 3 roofs combined?

What kind of thermostat? How often does the unit cycle, or does it run constantly?

In the five or so homes I have lived in, getting below 70 in the summer has always been a challenge. My current new system will drop the temp from 78 to 71 in less than 30 minutes but from 71 to 68 would take hours during the day.

I also have a sensi and it works great. I think your old thermostat may have been a couple of degrees off compared to the sensi and you are just trying to get the temp down too low.