[KILLERNADS]

So i have to completely rely on using the external video player, which works well but then has issues when you only watch half complete files, it doesn't sync this back with Kodi (ZDMC), and always marks the files are Watched!

Add this to the 'video' section of your advancedsettings.xml to regulate when to mark as watched:

<playcountminimumpercent>90</playcountminimumpercent>

This may not work if Kodi is only monitoring it's internal player and not an external although it's tracking something since it does mark iso's watched. No nfo's either. Give it a try. Keep in mind, an external player presents the option to resume from where you left off once it mounts.

Is there any benefit of playing 1080p files on a 4K device output?

That depends:

Yes, ONLY if you are using a 4k ACTIVE display.
You will render 1920 X 1080 to EACH eye which appears 4k (one eye + one eye = 2160) and the frame packed screens are also upscaled.

No, if you are using a 1080 display or PASSIVE 4k display.
The best a 1080 display will render is 1920 X 540 to each eye (one eye + one eye = 1920, and no upscale, you have no more pixels to fill).
3D passive 4k displays SKIP every other vertical line so it's end result is halved also.

Fwiw, HSBS is 960x1080 per eye, HTAB is 1920x540 per eye and FULL SBS is 1920x1080 per eye. (Half vs Full encoding)
Full is more advantages using Active 4k and renders 1920 X 1080 to each eye just like Frame Packed MVC.
Using full with passive will make no difference. It still skips every other vertical line as it does using Frame Packed MVC.

So I'm thinking of returning the Zidoo device, but if i do, i just don't know what to go for?!?

I can't help you with devices nor comment on them. I have no need for any of them. My home built Windows PC does everything all those devices combined can do and more, problem free in one unit, upgradable and highly versatile.

Any tips? I can continue to use my HTPC with the afedchin MVC build on it, but my HTPC windows 10 machine, seems to only allow output at max 1080p and not 4K?!

I am no longer able to use that build since upgrading to 4k either. I've reached out slightly but never got any replies on other threads so I use v.17 nightlies with PDVD.

Thanks for your detailed response. I will check a few things on the Zidoo such as the video players bookmark capabilities, should that work for MKV files aswell as ISO files or ISO only usually in external players?

What you suggest for adding <playcountminimumpercent>90</playcountminimumpercent>, i think only works for the internal player. I will try it, but i don't think Kodi knows anything about the external video player. So can not monitor when its start or finished watching a film. To be honest, i would be happy if its possible that when you come back from the external player to Kodi and click Okay for Playback has ended, that it didn't mark anything on the video at all, then i can manually mark it watched if i feel the need to! But i have no idea if its possible to do this?!

You mention you are using your own Windows based device? What kind of one is this? Im guessing you have one setup like i had my HTPC setup with the 3D MVC build. But the problem with my HTPC is that its about 6 years old, what would i need to upgrade in it to make it 4K compatible? Is it usually just the graphics card? Processor etc....?? I think that the GPU is probably built into the motherboard on this small device. I have to check.

However, with your build what Kodi version are you using then? Because the default Kodi doesn't support everything right such as Passthrough Audio for Atmos/DTS:X and 3D ISO etc...