Taking Toll Roads gets you to the congestion sooner and more expensively. The exception being the 30 from I10 to Georgetown.. There are still 'left lane louies' but at your speed won't be much of an issue.
North of Austin, Georgetown you will get to Salado.. narrow lanes and construction, not enough room for a couple of 18wheelers.. they knocked a bridge down on top of a Texas DOT worker..
So, I would 'exit' at Hutto.. where Hwy 79 crosses underneath it. The toll booth is snug but you can make it...
Oh, In "downtown' Hutto there is the 'Texan Cafe'.. pretty nice place.. and great desserts. It is on the North side of 79: