Turns out that if you go into Steam's settings and set advanced streaming device option (host) to prioritize speed solves the occasional frame drops.

So now I'm mostly using my Steamdeck as a PS5 Portal - like device to stream more demanding games to save on battery and processing. (running Baldur's Gate III locally drains the deck's battery in an hour at low settings, with fan noise loud enough to wake the kids. This also made it possible to chill on games like Ryza3 at max settings with relatively high fidelity when I'm home.)