If you are doing your punch in/out at the time you are recording the original track you should NOT have varying levels.

In fact, I have done punches several days after the original tracking was done and there is ZERO difference in levels.

Keep notes. When you track something, write down the numbers.... especially if you're using a mixer that is used for other things. That's what several people I know do.

Personally, I don't. I rarely touch the input levels and don't use a mixer. So there's literally nothing for me to remember.

If there are level differences, I drop a volume envelope into the track in my DAW and adjust manually.

You can find my music at:
www.herbhartley.com
Add nothing that adds nothing to the music.
You can make excuses or you can make progress but not both.

The magic you are looking for is in the work you are avoiding.