Cleaning the primary mirror of the 200P is very straightforward. If there is a challenge it’s prising out the mirror assembly as it is a tight fit in the ota. If you believe there is something missing or unclear in my guide, then let me know and I will update it.
As for collimation and concentricity of the secondary... The outer edge should be circular and concentric. It’s the reflection (it’s dark because it’s looking at the inside of the sight tube) of the secondary that is offset but it is still circular.
If the secondary is centred but still not quite circular and assuming your focuser is square to the main tube, you can either leave it as is and move onto the primary or you can keep tweaking to get it circular. I find loosening the assembly so it’s in my palm allows me to confirm there is a position that is just right.
As for which guide is right for you, I’d recommend reading as many as you can and picking out the parts that make sense to you. I came up with a=b nomenclature because using diagrams worked for me but were all learn in different ways so find one that works for you. Writing your own guide could be your salvation…