I edit with Vegas 17 pro. My computer is fast with 32gb RAM. Editing 10 bit XF605 mxf files is fairly sluggish in the preview window, which has to be in lowest rez mode to get any 'flow' to the footage. Would 64gb make a big difference? As in, would I be able to preview in full mode?

I watched this short video, enabled the recommended software, and my system plays back 422 clips without issue via the installed player and shows now a Windows thumbnail. BUT the files remain sluggish in Vegas. So what's the main issue? Here is the link https://youtu.be/Obf3j1bALY8

You've given lots of details that don't matter very much, but gone and left out the most important stuff . . . What kind of drive are your files stored on? How is connected? How fast does Blackmagic Speed Test say it runs?
And finally, what is the codec? 10-bit 4:2:2 covers a lot of territory.