I'm thinking of moving my main drive (system folder, user accounts and apps) over to an external SSD thunderbolt drive to speed up my 2017 Retina iMac (64gb ram) which has a fusion drive. Footage is on an external RAID which seems to be fine but was finding software sluggish. Is this likely to improve performance at all? Planning on upgrading in the new year but wanted an interim solution. Using Catalina.
What percentage of your system drive is left now as free space? That could be the issue. I do not think an external drive will be a viable solution. The cost and time involved to make that happen, not sure it's going to solve your issues.
It would be hard to guess what the bottleneck in your system is. A RAID array of 6 HD or more should work just fine as would a Thunderbolt SSD. Having said that every week a FCPX user will post about a choppy and sluggish playback. Is it the HD, the GPU, the CPU or the T2 Chip? It would be great to see FCPX users post their statistics. Some video files are huge and require a lot of throughput from the hard drive system. Other video files will require a lot from the CPU and others will take a toll on the GPU or even the IGPU. Depending one what you are doing you CPU could hit 100% while the GPU is only at 20%. Having said that you might have the GPU at 90% and the CPU at 20%. I know Intel's Quick Sync does not work with all H.264 video files.