After watching the stream for a second time, here's my first impressions:
Mazda Roadster S (ND) N200: Very lively, can't hear much of that dull sound they usually have.
Toyota TS030 Hybrid: Couldn't really tell with all the jump cuts, need more video.
Mazda LM55 Vision GT: Retains that fantastic sound in what seems to be a slightly improved version of that AES system put in GT6
SRT Tomahawk GTS-R Vision GT: Still has that oversaturated drone from GT6. Can only guess its still using the same sample.
Hyundai N2025 Vision GT: Well...like all the electric cars?
Peugeot 908 HDI FAP Peugeot Sport Total: Basically using the GT-R GT3 Sound from GT6, Turbo hiss and all.
Jaguar F-Type GR.3: Very Jag-like, about as good as the XKR-S Sample (which was one of the best samples in GT6)
Renault R.S.01: Sounds good, though not quite as Nissan-like (for lack of a better term) as its real life counterpart
BMW Z4 GT3: Miles better, actually sounds like a V8. They are clearly trying to mimic that distinct octive of that car, but its missing that additional detail that really brings it out.
Alfa Romeo 4C GR.3: Sounds like it has the sample from the Evo Rally car in GT6 (which I'm not sure if that is even right or is an attempt at a racing version of its Straight-4, the same engine as the Evo ironically)
Audi R8 LMS: Sounds good, abit more raw then GT6 but missing some meatier details
Toyota FT-1 Vision GT: Actually sounds closer to the real life TS030 then the car in game, which is..odd
Nissan GT-R GT3: Couldn't really hear it, need more footage.
Aston Martin Vantage GT3: Not quite V12-ish in some cases but the onboard seemed slightly closer (Though more towards the old DBRS9 then the Vantage). I definitely need to see more footage to be sure.
Peugeot Vision GT: Not really audable.
Corvette C7 Gr.3: As with the Ferrari (though much more clearly), sounds more like the road going car then a competition version like the C7 GT3 or the C7.R
Mitsubishi Evo Final Edition: The first car with that turbo chirp. Main sound needs more meaty straight 4 sound (Something that the Alfa has weirdly), but the turbo is quite crisp.
Mercedes SLS AMG GT3: Still the same sample from GT6
Volkswagen Golf GTI Roadster Vision GT: Haven't heard it once so unsure.
Mclaren 650S GT3: Sounds distinctly Mclaren, though could use a little more bass.
Subaru WRX Gr.3: Very much sounds like a boxer and appears to be using a improved version of that AES effect, just needs abit of tweaking. Turbo chirp just as good.