Labeling and filing at the same time?

We’ve purchased. It’s the greatest.

Is there a way to assign tags to a folder such that when you drag a source to the folder, the record is automatically assigned one or more tags?

No, however each tag automatically appears in the source list, and dragging onto the tag source will assign that tag. If you want to assign multiple tags at once you can type them into the tags bar at the bottom of the main window, use the Tags inspector, or use AppleScript.

EagleFiler 1.4 lets you do this using smart folder actions.