Thanks for the link, I came across that soon after your first post. For now I have a 1.5tb vdisk on a 2tb btrfs striped cache pool and so far it seems to be working great. I am transferring my steam library now so we will see what happens once it exceeds 1tb (Although I am certain it will be fine now that the data is striped). Once I have everything stable I will dismantle my old LXD server and use its SSD for the VM's OS, keep the cache pool for games, and use the rest of my disk for less sensitive data storage (mostly infrequently accessed Plex media and temporary storage). Not exactly what I intended but it accomplishes the same thing.
BTW, I did notice that each share can independently enable/disable the cache, which is quite useful for me.
Thanks for your help, I think I'll stick with unraid if everything looks good over the next few weeks. I am using the trial now but it looks like a license may be in my future (never thought I would pay for a linux distro, but lime-tech seems deserving enough)