New Final Cut 10.4 with OS High Sierra

From reading the posts on fcp.co and other forums, it looks like if you are upgrading to 10.4, you must also upgrade to OS High Sierra. This seems to cause the least issues. Both our edit rooms are OS Sierra with FCPX 10.3.4 Obviously
we want to be able to update the older 10.3 projects. Has anyone had major issues. 2 Mac i7s with 32ram with NVIDIA GTX 780M at 4096 MB Both hooked to Pegasus T-Bolt 1 and 3. (Machine 1 is 2014, Machine 2 is November 2017)

FCPX runs just fine on Sierra. You only gain ability to work with HDR and 360 video with High Sierra.

Sam from LumaForge stated during the Virtual Users Group (see Front Page) that they think they've seen Macs that have fresh installs having the least issues, and Macs that simply Upgrade have more issues. He didn't offer any numbers or actual evidentiary evidence to back up that statement. I've personally not found that to be true all the time.

You can very safely update to FCPX 10.4 on Sierra just fine. I'd check the tech specs before upgrading.
www.apple.com/final-cut-pro/specs/