RAM upgrade for an iMac 27" 2017 used for video-editing, compression and audio recording
I'm a big believer in having more RAM generally, but of course in many situations having more RAM isn't warranted. In your case, however, having more RAM is going to be useful because of the type of tasks you're using your iMac for. 

The key spec missing from your question, however, is the type of storage you have. If your iMac has one of the Fusion drives, then you'll get more out of your extra RAM than you will if you have an internal SSD. This is because macOS will use your storage device for virtual memory when it doesn't have enough RAM available.

In summary, if your internal drive:


is a Hybrid/Fusion drive, then definitely upgrade your RAM.
is an SSD, then strongly consider upgrading your RAM