This weekend I've had a unique opportunity to compare not two, and not even three, but four 2-1 transformers
2016 HP Spectre 13
2017 HP Envy 15
2019 Yoga 720-15
2020 LG Gram 13
Among other things I tested sustained 3D performance with TDM.
TL;DR Intel Iris does not make sense in 15W chips (well, it did not on 14nm)
https://docs.google.com/spreadsheets/d/1ujhtjCu477khi6LeeztGt_1sX2YC6LI-kUgk3lpLaMI/edit?usp=sharing