16” MBP M1 MAX SLOW PERFORMANCE

What drive is this? How is it connected? How is it formatted? How full is it?

There may be software conflicts - that is particularly more likely if you migrated everything from your previous mac.

We need information about that in order to help, so: Please run Etrecheck and post its full report here. Use the "additional text" button and paste the report into the text box.

WAIT!!!!!

You have that sworn enemy of video applications right there: Chrome. And, particularly, its nasty hidden minions, the "keystone" daemons that hog the system videotoolbox.

See https://chromeisbad.com for how to completely uninstall those pesky things.

After that you will need to drag FCP to the trash and download a fresh copy.

Besides the keystone things that we know cause trouble, the report is pretty clean.

Does FCP have "Full Disk Access" in System Preferences->Security & Privacy->Privacy? I assume it does already, but if not it needs to be added.

Also, there is a chance there is some problem with the library itself.

You could try a simple test. Close this library, make a new one on your external drive, add some clips, and make a short project.

How does that proceed? Are then slowdowns? If there are slowdowns, quit FCP and copy this test library to your internal drive. Test. This ought to be extremely fast.

Did you try creating a library in the internal drive? That ought to be extremely fast.

Also: if you run BlackMagic Disk Speed Test on your external, what do you get? By comparison, the internal should be some 500 times faster...

Your external drive (or perhaps the way it is connnected) is a big problem.

It looks like it is only using a USB2 connection. That is completely inadequate.

Your internal drive is over 150 times faster.

(EDIT: in my previous post, when I estimated 500, I meant to have written 50; thus it is three times as bad as I thought it would be)

I suggest you quit FCP, eject the external drive, and completely disconnect it from your mac.

Start FCP again. Still slow? I don't think it will be.

If you haven't already done it, try some new footage as there may be a corrupt file ruining the performance.

A couple of years ago I suddenly had problems similar to yours and found by a process of elimination one 4K video file that was causing it.

I trashed the file, reimported it and everything worked perfectly.

I'd look at that adapter. Can you tell us what it is, exactly?

It seems that your drive may be USB3 capable, but your adapter may be limiting it to USB2 speeds.

That would explain why the drive used to work fine on a USB3 port on your iMac.

EDIT: and if you were using the same adapter with an SSD, that would tell us why even that would not work correctly.

Note how it says: 1 * USB3.0 + 3 * USB2.0

You will need to make sure that the drive is connected to the USB3 port on the adapter.

They don't seem to be identified but an educated guess is easy to make.

I suggest you test with BlackMagic Disk Speed Test. On USB3 it should give you 100MBps or more for the HD, and perhaps 400MBps for an SSD.

Also: this appears to be a low cost adapter; it is possible that it may not offer the best performance, but still USB3 will make a huge difference.

You said that FCP X struggled to create a library on the internal drive. . . . did you have multiple libraries open at once?

If you haven't already done it, close every library, disconnect all external drives and then try creating a new library on the internal drive . . . it should fly.