Yes, I have tested a 9400f installed of the 9400t and was very disappointed with passmark scores being 1/3rd of the 9400t.
I have tested a p1000 and a A2000 on it.
And the BIOS would balance 100w as it seems fit between the CPU and GPU. Sometimes it's 30w to the CPU and 70w to the GPU. Sometimes it's 35w to the CPU and 60w to the GPU.
Mind you this was happening with a 230w original Lenovo power adopter. So it does what it does due to power delivery not due to the power adopter.
For P1000, did you test the original one that comes with this unit (single heatpipe, no fan) or an aftermarket unit with a small fan?
Official Passmark scores for 9400F and 9400T are close enough. It seems the unit is not able to cool 65w/non-T parts properly.
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Edit: just saw
@aasimenator's message.
1. Is the heatsink different between the 65w and 35w parts? I saw some mention of upgraded parts but might have missed it (sorry).
@Mann I checked the official Lenovo psref for P330 tiny and the 65w parts are indeed supported.
They list 135w power supply as the default but I guess 170w/230w units exist and work well as can be found in the Servethehome.com 'Reference thread'.