My two cents on this discussion, which I am following since a long time.
1) I have MacBook Pro (16-inch, 2019), with AMD Radeon Pro 5300M 4 GB.
2) After upgrading to Monterey, and using lpm, I notice a significant improvement (using a dell external display at work and a LG at home). With the lid open, I can have the GPU at ~6-7 W, while with the closed lid it goes down to ~4 W.
3)But, from time to time, it was going suddenly up to 18-20 W, without anything running in particular. I noticed that the big difference is given by apps using at some point (unexpectedly) intensive of gpu-rendering. In this regard, Chrome was the app with the highest impact. For example, after exceeding a given number of tabs, the gpu-rendering was starting to increase (also if the pages were apparently not supposed to require it). I noticed, that even pages showing github Actions pipelines, or gitlab, were increasing the GPU up to 20W.
4)The solution, in my case, has been to use as much as possible Safari. Moving most of my web usage to Safari, resulted in the load never exceeding the 12W, and always with a short duration of this activity, hence having a stable ~6-8 W with very short and are excursion (seconds) to 12 W, whiles for Chrome these excursions were more extreme, and lasting forever.
The conclusions base on y personal experience are:
1) Monterey with lpm does its job
2) whenever you see a sudden increase in the W of your GPU, have a look at the task monitor, and guess which application is mostly responsible (Chrome for sure, but also Skype, Slack, and WhatsApp might have a significant impact). Indeed, you might think that your GPU is going crazy without anything really doing graphically demanding jobs, but some tab of your Chrome browser (open on a light page, but with some weird js code) might actually be responsible for the intensive GPU task