As mentioned above the answer is yes unless specifically outlined otherwise in the user setup screen under the owner profiles settings screen.
Even allowing apps to run in these users in the background however doesn't mean necessarily they will always remain running and all apps and processes are subject to Androids resource management and maybe closed etc should requirements be needed in other users or the owner.
Concurrent users are also limited by device/RAM.
If you End Session on a user this also removes it from running in the background and put's the user back at rest/encrypted.