Need to remove things from 'Files'/iCloud on my iPhone

Hard to say. The first thing to do, would be to determine how they got onto iCloud or iCloud Drive

If you enabled say, Documents & Desktop from the iCloud Drive options on the Mac for instance, the only way to remove them from iCloud would be to disable that option.

If you did something else, then you need to determine what that was before anion can tell you how to delete them without affecting their counterparts on the Mac.

Note, them being on iCloud does not automatically mean they are downloaded to your iPhone. They can remain in iCloud and will show a small cloud icon if they are not actually downloaded to the iPhone. They would only be downloaded to the iPhone if you attempt to open them in some way.

iinami wrote:

Thanks. I probably enabled Documents & Desktop from the iCloud Drive options. If I just disable that option from my MacBook would they still stay in their current respective folders on that MacBook?

Yes.

Would I no longer see them in the Files app on my iPhone? That sounds like the easiest option.

They should stop being visible in the Files on the iPhone yes.