No, it won't be an accurate representation or the performance of Proton/Wine. The only way to get it to be somewhat accurate would be to do a GPU pass through, even then it would probably still be quite inaccurate.
What I would recommend is to create a partition on your drive and install a Linux distro such as Ubuntu. I wouldn't recommend installing it to an external drive as the speeds will be horribly slow, and I also wouldn't recommend trying it in a live "test it out before you install" environment. Make sure you get the correct, up to date drivers for your graphics card. I know it seems obvious but I once spent three days trying to get Minecraft to stop screen tearing and lagging and my drivers were the issue.
My final point: this is one of the most well written questions on Reddit, you thought of everything! I wish I was capable of writing such well thought out questions!
That's dope! How much storage have you got there?