I am driving Yaris 1.3 Ativ CVT for a month now, drove it on motorway @ 120 - 140. I looked for any noises but didn't notice any. The engine does get louder if gas pedal is pressed hard otherwise it can go to 120 gradually with almost no sound. I haven't changed stock tyres yet but I think changing them will further increase the quality of ride.
IMC is selling 1000s of units every month, I do agree some units will have QC issues (which is annoying for a new car).
I own Honda City 5th Gen and Corolla 1.3 2017. I can compare Yaris with them, the ride and build quality is far better than City and somewhat comparable to Corolla.
I can do a round trip to from Lahore to Islamabad in one day on Corolla but for Yaris and City I'll have to think twice 