This is a very good review. I have 2 suggestions:
1) Please add the 7745HX Legion in the comparisons as well as the 13700HX Legion.
2) Get in touch with Allen Ngo to see if he is using different methods in some of the measurements. He has measured the 7745HX as significantly quieter under full CPU load and the idle temperatures as even more significantly lower. In fact, I reviewed all of Allen's Legion reviews and he seems to be consistently returning lower full CPU load noise levels than Legions reviewed by anyone else.
I just received the 7745HX version with 4060 and so far so good. With discounts I got this for about $1k. This was just $100 more than the 7645HX with 4050 reviewed here although both are for the 300nit screen.
I previously had the 2022 Legion 5 Pro 6800H with 3060 and then the Legion Slim 6800H with 6800S. Both died on me. So I was a little worried about getting another AMD version but compared to the 13700HX, the 7745HX seems superior in almost every way.
I was also a little worried about dropping down to the 300nit screen from the previous standard 500nit but so far I don't see an issue.
Although the entry level screen brightness and lack of Thunderbolt / USB4 are a backward step, the 2023 AMD version for me is a significant improvement over the 2022 models I returned. CPU performance has caught up and is on par with Intel and fan noise and external temperature is down for everyday computing. On top of that, the Lenovo software seems to have matured. For example, the 2022 models were not keeping the battery from charging above 85% but my 2023 model is. Also, the ports have improved a little as there are USB A & C ports next to each other on the back and left side.
Apart from that, the interesting thing in this review compared to the Legion 7745HX is the better performance in PCMark for the 7645HX, whereas other benchmarks seem to behave as expected. As mentioned, the external temperatures at idle are also significantly different and while the fan noise at full cpu is also different, I suspect that is a consequence of Allen measuring differently to other reviewers.