One way to do it that makes it nice and simple is to create blueprints of the templates - go into the template, select all the actors you want, then from the Blueprints Menu select “Convert Selection to Blueprint Class”
Then you can just right-click that from the content browser and migrate to your project - it handles making sure all content required by the new Blueprint is migrated.
The downside to this method is then to edit it (eg the walls) you need to edit the Blueprint rather than in the actual level.
I’ve got a tool on the marketplace (rdBPtools) that extends the “Create Blueprint from Selection” to give more features such as ISMs and randomization - and the ability to copy everything back to your level as individual actors - then it’s easier to edit them - and convert back again later if wanted…