Workers should be picking up qbwrk.conf regardless of the mode in which they are running. Confirm that you don't have autostart set to "service on boot" (which is the default). It's possible you're starting both the service and the desktop worker.
To check this, you'll need to go to each computer (or at least a sampling of a few), open the GUI, then go to Administration > Autostart Worker: xxx > Enable Desktop User. Do this, then restart the GUI and see that it's still set to start on user login. If it reverts back to "service on boot", then the running user doesn't have permissions to change the service. You can try running the gui as an Administrator (right-click the Qube icon > "Run as administrator"), or you can log in as an administrator, start qube, then disable autostart.... then re-login as the user who should be running qube and set the autostart to be desktop user.
Alternatively, Assuming your workers are Windows, you can go into the Services control panel check that the "qubeworker" service is not running & not set to auto load.
Important Note: When running in desktop user mode, you *MUST* set the "disable_windows_job_object" job flag. I strongly recommend setting this as a supervisor_job_flag on the supervisor - this will force all jobs to use that flag.
Workers that report they are missing the jobtype _3dsmax are, in fact, missing the jobtype. You'll need to install the jobtype (and Perl) on those machines. You can determine which machines they are by going to the workers tab, clicking a worker, then scroll to the bottom of that worker's Properties tab. You will see a list of available jobtypes. Some of them will be missing the "_3dsmax" entry.