Intune Confusion

Hey guys, 

I'm relatively new to Microsoft Intune and have been playing with the platform with a view of potentially using it as our corporate endpoint management solution. 

I've been playing with it for a few days and I'm a little confused. 

Within our organisation we have about 25 'hotdesks' shared by Call Centre staff working on shifts - I thought that Intune Plan 1 Device Only would be a good fit for these systems. For the remainder of our staff (circa 250), I was thinking maybe Device Only or maybe User license. I'm not sure we require a full user license for everyone as we have a small amount of corporate software (so no real requirement for corporate software catalogue within the user portal etc) and only really need to manage Windows updates, configuration / security policies and to push / remove software - which I 'believe' is possible with the device only licenses. 

I've started off by acquiring x4 device only licenses (thus have not assigned them to any users) for testing purposes. My 4 test systems were already AAD joined and so to enroll them I did this using by a Device Enrollment Manager account and joined through 'Settings > Accounts > Access work or school > Enrol only in device management' on each test workstation. All 4 test systems enrolled without issue and are visible within the Intune Portal and are checking in. 

This is where I get confused:

1 of the 4 test workstations has the IntuneManagementExtension service running in Windows. The other 3 do not. The system that does have the service running also has the IME log directory present = C:\ProgramData\Microsoft\IntuneManagementExtension\Logs - the others do not. Again, all 4 systems are enrolled and checking in and reporting as compliant. Also, I've pushed a test piece of software to all 4 test systems (mandatory push)... none have received it. This was 8 hours ago. 

I also noticed when running dsregcmd / status that the MDMurl was blank on these workstations. 

I have a personal M365 tenant with Intune Plan 1 user licenses that I've used for a year or two and have had no problems or oddities experienced with software pushes (probably not oddities but more of a lack of understanding of device licenses on my part perhaps). I checked one of my personal workstations and they do have the Intune service running and the logs directory. 

Can anyone shine any light on why:

A) One system has the service running / the log directory present and the others do not?

B) Is there something fundamentally wrong with my understanding of device only licensing perhaps? Is there something wrong with the way in which I have enrolled these systems perhaps?

C) Any idea why the software would not install on any of these 'device only' systems (nothing is being reported at all RE the deployment in Intune and I deployed the software about 8 hours ago)? 

D) Why would the MDMurl be blank but all systems are successfully checking in?

Any pointers appreciated as I've been tying myself in knots with this. Pretty certain this is due to a chronic lack of understanding on my part.

Greatly appreciate any assistance guys.