Huh weird, I haven't had an issue with Steam for a long time, and that's on both NVIDIA and AMD. Granted, this is on a desktop, not a laptop, so if there's any kind of issues switching with the iGP, I'm not going to see it. I've also never had an issue with download speed, but my Internet connection isn't super fast anyway (just 50 down).
My issue is that Heroic doesn't seem to fix controller issues, so games are hit and miss on my Steam Deck. It works fine on desktop though.