I see things differently coming from racing C5Z06. I would go back to that in a heartbeat. I have had nothing but pain and big expense from my purchased new 2019 GT gutted into a racecar. This is the worst car I have ever owned from a working on it standpoint and I have worked on cars for 45 years. It is the worst car from an eating consumables standpoint. The vette consumes like a 4 cyl economy car compared to the S550 tire eater. The s550 eats race tires twice as fast as the vette!
My disposable track car is a 2003 C5Z06. I say disposable because I want my track car paid off, I don't want to have to purchase track insurance and if something bad happens I can park it with no drama.
Personally, I would base my track car of choice on factory horsepower first. Unless you are a master engine builder and have the time and skills to do it right, trying to get more horsepower out of a street legal vehicle that is going to be used on track is a recipe for disappointment. The amount of engine failures from shops that are considered "guru's" is shocking. You rarely hear about this because eventually the guy with the "money pit" is going to try and unload the unreliable beast on the next guy. So I make my purchases based on what factory horsepower I want and never crack the engine open (no heads, cams, turbo or supercharger upgrades). I need to make sure the car will stay cool and stay together for a minimum of 25 minute sessions when temps approach 100 degrees. Exhaust and intake upgrades are ok, but if you have a shop crack the engine open to do internal mods, good luck having ANYBODY stand behind the work for a car this essentially doing a 25 minute dyno sessions....five times a day.
I started with a 1999 Mustang with the 4.6 engine....highly modified suspension and drivetrain but stock motor. You cannot hurt that set up (it only had 260 hp) no matter what you did or how hot the ambient temps were. It was a great car and I should have never sold it but kept it so friends could use it at the track. Super easy to drive and super predictable. I wanted more horsepower so I moved up to a C5Z06. Again, highly modified suspension, brakes, drivetrain, etc but engine is bone stock except for the removal of the cats. I still run the stock LS6 manifolds and stock mufflers. It does have lighter weight race seats but also a custom welded roll bar by TC Designs which is probably 50 to 60 lbs (just guessing). It has full interior, working A/C, stereo, etc. With 220 lbs in the seat and a full tank of gas I weigh in at 3384 lbs. I'm on Nitto NT-01 tires and can keep up with Mustang GT350's....except on very long straights where they pull me. And as a driver, I'm by no means fast...the car is definitely faster than my talent.
If I was to do it all over again, I would have saved up for another year or two and gotten into a C6Z06. With the correct suspension, brakes and tires....that car will keep up with Porsche 911 GT3's (if drivers are of equal talent). Once the heads are addressed leave the engine alone...the revving ability of the LS7 makes it a true track monster since you shift less often and it lets you keep up with those pesky PDK's. And the C6Z06 is even lighter than my car. It's easy to get a full interior C6Z06 under the 3000 lb mark with 505 factory horsepower.
If I was going for a new platform with a full factory warranty, you cannot beat the Camaro SS 1LE platform. Aftermarket parts availability is absolutely huge and if you want to play with the motor, nothing is cheaper than LS parts. How GM made those cars handle so well at their weight is impressive. Being a four seater, you can even haul kids around if you needed to. I personally like the looks of the new Mustang much better, but for a very track focused car, I'd stay with the Camaro. If you have a higher dollar budget, then the C7 Grand Sport is top dog IMO.
Personally, I feel a track car (for HPDE's) that weighs over 3000 lbs has to have at least 400 horsepower to keep me interested. I really try to keep the weight low as it really helps with consumables and overall reliability on the track.
If the stock horsepower of a BRZ will keep you happy, then it would make a very fun track car. I've tracked with a few Miatas that had just over 170 hp and full aero and wings that I was barely able to match in track times. Talk about a package with very low consumable costs.
Good luck on whatever choice you make!!