Hey, US citizen here who just re-entered the USA thru LAX.
In short, I did nothing abnormal aside from use the CBP app to generate a QR code to speed up immigration. Turns out they weren't doing QR codes or global entry or anything at LAX. So all US citizens were in a very long line with only 1 TSA agent processing people.
So I would prepare for a long queue. But Im a US citizen so that makes a big difference in your level of scrutiny.