They can get a lot of HP out of OHC. As to throttle by wire, I have not looked at it, have not looked at the air filter but was supposed to have been recently changed. So no IAC or cruise cable/box. I cannot get comfy with the NON replace PCV though. Still has a tranny dip stick and belt driven water pump. I hear bad things about water pumps inside the engine, even those off a timing belt.^+1. That drive-by-wire throttle is a different animal, lol. I have it on my '12/'13 Impalas. I've been told to never work the butterfly by hand to clean as it can be damaged. Supposed to leave it hooked up and open/close with the accelerator. The Impalas have the 3.6 VVT DOHC LFX engine with 6-speed automatic. I like the 305hp. They're not as pretty as your Buick and probably don't have near as comfy ride.
As to comfort, it is very good, very quiet. Old coots kind of car.