Both front and rear panels work fine - still obviously cannot differentiate between headphones and speakers but quite happily moves sound playing to headphones when plugged into the front panel.

For reference I was using the generic Win 10 drivers before doing this and had completely removed all previous Realtek drivers using DDU in safe mode - this part is important if you are already on another Realtek driver.

Anyway, here is the driver link that fixes all the issues and I hope it helps others since neither Realtek or AsRock seem to care:

The little pops and click interference noises have come back, it seems that whilst this driver did indeed at least allow the front panel to be used for headphones (others were just a distorted mess - especially the latest version on the AsRock website), there's still an underlying issue with either this board or most likely some software problem that AsRock just keep 'throwing over the fence' at the other guy.
I'm hearing these pops and clicks via my desktop speakers (Harmon Kardon Soundsticks 3) plugged directly into the motherboard port on the rear IO panel.
Headphones on the front panel do the same thing, so I am 100% ruling out everything other than a software problem. I've ran latency mon, all the other temporary fixes - but they are nothing but bandaids to a problem that's not being addressed.

I know that with so many hardware and software components it's complex, but AsRock just don't want to even acknowledge the issue. In their very own user forums.

So, back to plan B which is to order a discrete PCI-e sound card for my needs.

Many can maybe 'live' with this issue as it's something that perhaps only someone who listens to a lot of music hones in on. For gaming, you may never hear a thing.
But these boards/sound options are sold and heavily marketed as upscale options that promise to satisfy music listeners and the reality is that they just don't.