^ As far as the unlocked frame rate question goes it is interesting to think about. Forza 5, Driveclub, and Forza Horizon 2 are really difficult to drop frames in during actual gameplay so they are either really well optimized to their target frame rates or just have a lot of overhead. I would guess the former though, as you can make at least driveclub and horizon 2 drop frames in Photomode with multiple vehicles on screen. I think in both those cases the game is just really good at keeping the amount of assets on screen at the optimal level to not drop frames (Photomode in both bumps up LOD models in multiple car situations), so I would guess they wouldn't run that close to something like 60 fps if unlocked, but probably somewhere in the upper 30s.
But LOD would not be bumped in game, because Photomode in these games is trying to achieve a bit more than what the engine are able to do in real time.
So, it doesn't really tell anything about what their framerates would be during gameplay if unlocked.
Seeing that weather effects put a 20-30 fps hit to pCARS' framerate, it wouldn't be crazy to assume that the weather effects in DC or FH2 have a somewhat similar cost, and so that they could probably run 20-30 fps higher without the effects, so anywhere between 50-60 fps.
Yes, both games from Turn10 and Evolution Studios, as they're exclusive titles to their respective platforms, are probably well more optimized than pCARS can be on the same platforms. But in the meantime, we could also argue that the weather effects in DC - I especially think of the droplets physics simulation on the windscreen - are much more demanding*, and would hit the framerate more.
* I hereby acknowledge the fact that the water sprays are certainly very demanding and are going all in in pCARS, whereas they are toned down in DC. But I'm taking my 20-30 fps drop in pCARS from the DF video where we can see that happening on a wet track with no cars ahead, so no water sprays to render.