I haven't bought rain tires so unless arcade mode automatically puts rain tires in rain races for your personal cars then no, I was still on my comfort tires. In GT7 it seems like you will have to buy each of the tires you want in the parts store.
Comfort tyres are actually pretty good in the rain. If you want to try aquaplaning, get Sport or Racing slicks.
The right kink after Eau Rouge at Spa is notorious for having puddles in the rain (at least in ACC, it always does). That would be the first place I'd test for aquaplaning. It's at high speed so you won't confuse aquaplaning for usual wheelspin. If your car doesn't slide across the track then aquaplaning isn't simulated.
I'm loving the mix of new and current cars. After GT Sport I was a bit doubtful as to whether PD would actually add more recent cars but they have. This is GOOD NEWS and I can't wait to see what's next.
I'm the opposite. PD is 1 or 2 generations behind on current cars (as they always do).
No Alfa Giulia.
No 2nd Gen Audi R8 or RS6.
No New Vantage/DBS SL/Valkyrie.
No New M4 (or M2/M5/M6/M8 for that matter).
No Chiron.
No C8 Corvette.
No SF90 Stradale or 812 Superfast.
No i20N or i30N.
No Centenario or Sian.
No MC12 or MC20.
No 600LT/720S/Senna/Speedtail/Artura.
No AMG One.
No 918 Spyder (despite having LaFerrari and P1 GTR) or 992 GT3.
No Levorg or New BRZ (literally just a bumper change on the GR86).
No New Teslas.
No Mk8 Golf GTI/R.
And still missing critical brands like Bentley, Lotus, Koenigsegg, Caterham, Volvo/Polestar, Kia, Holden/FPV...
I love old cars but PD has never been up to date with new cars (except Japanese brands) and it's the same with GT7.