PeteHski

It sounds like you are in danger of overthinking this.

I'm sure you would be able to fit on either frame size - most people have a choice of at least 2 frame sizes. Preference for a smaller or larger size depends on how aggressive you want the fit and bike handling. Pros tend to size down for a more aggressive fit i.e. more bar-drop and then fit a longer stem to get the reach. A larger frame allows a more relaxed fit with less bar drop. Bike handling is also usually slightly more stable on a larger frame with a longer wheelbase, though probably not a big deal.

Saddle height - I would start off with the lower recommended height and then adjust it yourself to suit. Going too high will cause more problems than being too low, so better to start off conservatively. Perhaps the first fitter had taken into account that you are a beginner. A very experienced and well-regarded UK fitter made an observation in one of his videos that most cyclists he fits arrive with their saddle set way too high. He put this down to our culture of "looking pro".

Bike fitting is not an exact science and is full of conflicting opinions. As an experienced rider, I do my own fitting, but I do occasionally talk to local experienced fitters and read up on the subject and the advice out there is not always consistent and sometimes directly conflicting. As a complete beginner I do think you did the right thing consulting 2 different fitters, but I wouldn't take either of them as gospel - just consider them a half-decent starting point. At this point you just have to start riding and see how you feel on the bike. It takes time to take it all in and get a feel for what you really like.