For reference on the speed of these things, I couldn't find a GT3 lap of Interlagos, surprisingly, but I did find the lap times for a Porsche Cup car, and the lap record of a GTE Porsche 911 RSR from 2014;
Porsche 911 RSR (2014); 1:30.101
Stock Car Brazil V8 (2019): 1:37.631
Porsche Cup (2012): 1:46.762
Porsche Cup (2021): 1:36.362
Now, I realize that is not the greatest comparison. I'm not sure how much the Porsche RSR has evolved in 7 years, I'm sure it's a lot though, and the 2012 Porsche Cup would have been running a manual-sequential transmission, unlike the paddle-shifted semi-automatic transmissions of the 991 and 992 variants we have in iRacing, but the point is, these cars, despite being a "Chevy Cruze" and a "Toyota Corolla", are no slouches. They're powered by an LS3 V8, and in 2019 they brought one to the Bonneville Salt Flats (as they should every race car, ever) and they hit 214mph.
While Chevy is not the only manufacturer, make no mistake about it, this is a Chevy-powered league. Until the mid-2000's this series ONLY featured Chevy cars. Pugeot, Mitsubhish, and Volkswagen have all thrown their cars in the ring, but none of them have had much staying power and had all fallen out by 2017. 2018-2019 were back to only Chevy cars making starts in every round of the season, until Toyota came to the series in 2020. That probably explains the heavy influence that NASCAR has on this series, although I can't find any direct ties - this isn't NASCAR Pinty's Series (Canada) or NASCAR PEAK Mexico Series - it looks like they just borrow a lot of their ideas from other series, mostly NASCAR, but also they took a lot of cues from DTM, as is obvious from the outside shape of the cars. They also have Push-to-Pass, and maybe DRS (P2P may have replaced DRS)?