Your system will not work as good without enough refigerant. It will work a little better with some extra, but not too much extra. Look up pressure temp charts for the outside temp and It will give you pressures. I shoot for a higher temp on the high pressure, but you don't want to get your cold side over 55PSI or so.

The more pressure on the hot side the hotter it will get. It will have a larger Delta T and reject more heat. So the cold side can get even colder. But by increasing cold side pressure it does not get as cold.

IF you have a gauge set to use you can diagnose the compressor and evaporator. what were your pressures when you filled the system?

If the charge is too low it will cause the system to freeze up. Unless you have other problems.

Also have you cleaned or replaced your cabin air filters? That makes a huge differance on air flow.