As for me, I pay an extra fee to have boundless data in my personal home network. But for anyone without that choice, data utilization is a big element for Stadia games.
In terms of data usage, it will of course change based on your quality preferences. If you're aiming to play Madden NFL 21 with Stadia Guru at 4K then you're probably looking at about 16-20GB of information usage per hour. As this is a game you can play solo, on line, or anyplace with friends on the same Stadia link (via Chromecast with multiple Stadia controllers or on mobile or a PC browser with multiple controllers plugged in), it's impossible to know precisely how much information it will suck since hours will change for everyone.
I played Madden NFL 21 on Chromecast during my 4K TV, on PC at a Microsoft Edge Browser, and on mobile with the Razer Kishi and using just touchscreen controllers. Unexpectedly, Madden is really very playable using touchscreen controllers as soon as you get accustomed to where the virtual buttons are located. I'm still frustrated that I can not remap or alter where the buttons are on my display since doing things such as holding R2 to sprint are awkward when you would like to also be able to cover up the ball before an impact or immediately juke with the perfect stick. In regards to the fundamentals of playing though, you can finish an whole match on Stadia using only touchscreen controllers if you wanted or at the very least perform some management functions such as admin work or undergo transaction offers.
Check out https://www.mmoexp.com/Nfl-21/Coins.html/ for more details.