How long - From landing in Paris, thru customs, and taxis to St. Lazare station on a Friday

The standard advice on this board is minimum four hours between landing at CDG and departure from a Paris mainline railway station, though of course there are no guarantees.

Early morning is a peak arrival time for long-haul international flights to CDG, since there are overnight flights from the Americas, Africa and Asia, so immigration lines can be on the long side.

Customs is just a walk through a door that says Nothing to Declare. It is immigration/ passport control that has lines.

Thank you for the reply's. A couple of questions.

The best train for us leaves St. Lazare at 8:44. The earlier reply said the standard quoted time is 4 hours. Realistically, can we make the 8:44?

Since we are coming from the USA and aren't "premium" travelers, I assume we will need to get in line to enter the country, even if we don't have anything to declare. Correct?

06:00 + 4 hours = 10:00 No hope of catching the 08:44 from St. Lazare.

I assume we will need to get in line to enter the country, even if we don't have anything to declare. Correct?

There two separate checks made when you cross a border:
1) Immigration (aka passport control) - this is the check on people, whether you are allowed into the country, and for how long.
2) Customs - this is the check on goods, the contents of your luggage, whether that contains anything banned or taxes need paying.

Customs takes zero time if you have nothing to declare. You just walk through, they do random stops only (< 5% stopped).
It is immigration which is the major check and takes the time (30 to 90 minutes).

The order is : disembark - immigration - luggage reclaim - customs - exit

. Realistically, can we make the 8:44?

Only if you are good friends with a Star Trek Captain and they will let you use the Transporter system.

Even then, if there is magnetic ionization storm, I'm stuck. I'll settle for the later train. Thanks.

The later train at 10:09 even saves you a transfer, so it is better regardless. Plenty of cafés and bakeries IN Saint Lazare if you happen to be early.