I live in Steiner, and work downtown. That is a cluster**** of a drive when school is in session (620 to 2222 to Mopac). For various reasons, I occasionally take the 620 to 71 to SW Parkway to Mopac (or reverse).
The bottleneck in that route is through Lakeway, which seemingly out of spite refuses to do anything to properly time their stoplights. Heading south on 620, once you get past Lake Travis HS, it's clear. 71 to SW Parkway and on SW Parkway is easy. Same coming back the logjam is getting through Lakeway.
School-wise, the Steiner/River Place schools are better than Lake Travis or Dripping. But it's not a quantum leap. If you check the US News, etc. rankings, for public schools in Austin area, it's Westlake, then Westwood, then Vandegrift (which Steiner feeds to). There's actually a drop to Lake Travis, but that's still a great high school. Dripping is up and coming, but there are also commute issues from that area. 290 to the Y in Oak Hill is a mess, and RR 12 cutting to 71 is a 2-lane road. You mentioned Circle C, which is a nice area, but Bowie HS (though great for Austin ISD) is a far drop from the others.
You can make the commute from Steiner in 40 minutes barring a wreck. The easiest commute would be to get south of Lake Travis HS, to maybe Falconhead, Falconhead West, or areas around there. Just depends on where you want to live and what schools you want.