Hi Peter,
I generally use the focal ratio more for myself to work out if the scope may have coma with the faster scopes (lower f number). Some eyepieces do well to correct for the coma or you can use a coma corrector if you are bothered by it. Some people do not like the seagull effect of stars as you view progressively out from the centre of the eyepiece.
The focal ratio plays a bigger part I have found with larger aperture scopes as longer f ratio means a step ladder/ladder to view.
I like goto but its also a philosophical discussion as others prefer a more simple approach as the goto you will need to align the scope. Goto can be used manually as well.
Yep, the atmosphere is the transparency and seeing on a given night - it will be noticeable as you try to push for higher magnification. The image will go soft.
If you want to view planets, i found the seeing/transparency more the limiting factor - as the magnification you can used is dependant on this. Your scope's aperture will also play a part in terms of what constrast and detail you will see.
Hopefully these links might help explain a bit better:
https://www.astronomics.com/eyepiece...ication_t.aspx
https://www.cloudynights.com/topic/4...s-of-aperture/
Alot to pick up and I am still learning myself
Regards,
m11