Had a chance to try the new Pure LCS tonight and for those with a similar use case to mine, I'd recommend sticking to Gamma for now (latest version is fine).
I'm on an HDR10 panel (LG OLED) and LCS produces a very washed out image at the moment. I have all the HDR bells and whistles enabled in the DXGI panel of CSP, and enabled Pure LCS in WeatherFX. I think Peter mentioned somewhere above that only Pure and Pure Candy PPFs are currently supported with 0.4, but I tried both of those as well as AEGIS and PureHDR and pretty much everything looks unnaturally bright and strange. Going back to Pure Gamma in the Weather Controller fixed everything right up (with AEGIS or PureHDR) and had the proper HDR tone mapping again.
So I'm sticking with this version of Gamma for the immediate and medium-term future, and I'd recommend all others on true HDR10 panels do the same. Very interested to check in on LCS as time passes, but it looks like for my specific use case it's a no go for now.
No worries, I've read the documentation and understand its advantages, and further understand the annoying undertaking a Pure re-write for it is. Thanks again to Peter for this essential graphics mod.
One more note/question on this post - I've tried for a while to force Pure lighting on in online races, whether hosted by myself or in leagues or pubs. It always either defaults to an ancient version of Sol or nothing at all. Is the controller for Pure server side, and if so, how can I enable it in AC Server Manager? Cheers to anyone who may know.