If you reach out to Bambu Lab support, I’m confident they would kindly share the same advice: when using the chamber heater, it’s best not to place any AMS unit on top of the printer.
Also, it’s not quite accurate that you would need longer PTFE tubes just to position your AMS units on either side of the printer. Naturally, this depends a bit on how your setup is arranged, but the standard tubes are generally long enough to place the AMS on the left or right side without any issues.
My warm recommendation would be to avoid placing AMS units on top of the printer if you’re using the chamber heater, as the heat tends to transfer into the AMS units and could potentially lead to unexpected issues.