If anything, S397 has ADDED details & textures to tracks which increases the texture limits. I think your hunch about the 4GB vidcard is correct. Almost all the new tracks, especially the laser scanned ones, will easily exceed 4GB. Even 6GB is getting to be very crowded.
I have a 2070 Super with 8GB. You should try reducing texture detail because 4GB are not enough as you're guessing.
I have recently switched to Low texture details to reduce that Vram load. I can't notice much difference visually to be honest with the latest DLC tracks but I presume the older content would look really bad at Low settings. My PC is pretty much up to date with reasonably high specs, except the GPU which is a few years old. I am looking at something like the RTX 3060 but those prices haven't come down enough for my liking yet.
I am using a RTX3080 with a triple screen setup at 1440p and having most parameters maxed out - sometimes the FPS drops to around 90 to 100 but most of the times it stays at 144 (Nvidia sync for the screens running at @144). I need to watch it but I think most of the tracks are using 5 to 6 GB of VRAM; also NoS is requesting a bit more. So 4 GB might be not enough and I think lowering details will not necessarily lower VRAM usage.
start Daytona last of the grid, with night, rain, and 20 AI, you will have 30fps....and sometimes it's 90 to 100, no true at all, or you don't talk for official the s397 tracks and cars.....and it depends of the track conditions. I play all at max (all max even Anti-aliasing), and it's sure I need more power, and when I say more, it's like 100% more at least, I guess, I need the rtx 5090...
I know about Daytona but I would say that's worst case and even with no rain and with daylight I get 80 to 90 FPS "only" ... but I think this is based on Daytonas layout and scenery: we have those trucks behind the fences, grandstands with lots of people watching, the pits, garages, a lot of track lamps / lights and son. So I agree with you if it comes to Daytona. And I have to say I am also a guy who needs to know that there is "detailed gras" at race speed of 250 km/h ;-) But if we lower the settings a bit also Daytona runs smooth IMHO.
There are odd disparities in performance from system to system, even when the hardware would indicate that this should not happen. From discussions on Discord, with no clear and apparent reason, people report 50% less performance than others in, virtually, the same shoes or even with worse hardware. There are even some reports of people gaining performance by increasing eye-candy and bumping up their settings!!
The community I am member of consists of two other members using HP G2 whereas one of them has got less performant hardware; they compared their settings and driver version and the one with the more performant system has spikes and peaks whereas the other driver not ... Also I noticed that lowering e.g. circuit detail does not increase FPS as expected but does lower GPU load (in my case) and it seems to be much track dependent.
V1.17 Hotfix Update released: Tweaked anti cut and corkscrew apex 1 curbs Fixed some floating bushes Tweaked Second Apex Corkscrew Curbs Faster AI settings Fixed Heavy.rrbin profile not loading AI tweaks to corridors in pitlane and pit exit Fixed AI braking joining pit lane and improved AI line at corner after limiter Reduced Pit Speed Limit to 45mph Tweaked AI to reduce chance of AI hitting fence when leaving rear paddock Removed collisions from Pit Lane props Fixed secondary map tiling on corkscrew adv panel
RF2 Laguna will be need an update in few months the famous track will be renovated !!!!! https://racer.com/2022/11/09/laguna-seca-starts-track-renovations-to-mark-65th-anniversary/
So is MID OHIO! That is at least 3 major U.S. tracks that have, or are currently undergoing renovations/repaving.