On Samsung's N10+ Android 9 and 10 it doesn't throttle anything but will shutdown background apps* you're using. Most will shutdown themselves if not in active use. I tried many different settings configurations. WYSIWYG.I have generally found adaptive Battery only throttles performance but doesn't really offer a significant benefit in battery life. My experience with it has generally been tied to Samsung devices though so I was curious if there was any difference on Pixel devices.
I am of the opinion that if you let a chip work as fast as possible it completes tasks faster than throttled and that actually helps with battery life. Basically throttling may give you a slight battery advantage but the difference is generally insignificant but the hit to performance is generally real. So you get almost the same battery performance but better overall performance without any adaptive Battery features enabled.
It will be interesting to see the results of your test to see if my experience is true or if Google has implemented a version of adaptive Battery that actually works and gets better over time.
It's not a Samsung service although it's accessed through Device Care.
*some say this behavior can be adjusted but I never tried to reason with it. Best SOT and deep sleep state are my guilds to optimizing... everything else is in the way.