To deal with this as 3 separate points -

1. Not me but my wife. She is a graphics designer. She cannot remember now why she chose Producer instead of Gold (which she had first). Basically if you don't say to yourself, while using the free programs, I wish I could do this then you don't need the higher end program. We don't know at this stage which version of PTE AV we might end up using but the Studio Pro has 'Quick style for slides' and 'Envelope tool (keypoint control of sound volume'. The standard version, Studio, doesn't have these. We will find out. As an aside the writers and sellers of thee programs always want you to find a reason to have to upgrade by putting some useful things into the Pro versions as an enticement. If you don't need these things then don't buy it.

2. She wants a program that handles 4k for the whole show. So anything that goes in needs to be high resolution. If you shoot 4k video then why downgrade to HD if you don't need to. Same with photos. No sense in downgrading the photo quality if you don't need to. She has already processed a few samples at HD and showing these on a 4k TV you definitely notice HD stuff isn't as sharp.

3. As I said my wife is a graphics designer. She notices things that maybe you don't. And wants things that maybe you don't. Hence you both have very different needs. One of these is resolution. If your TV is HD only then you will be satisfied with less. We now have a 4k TV and sharper is better (for sharper read higher resolution). We accept the fact that if we are showing the slide show on somebodies HD tv it won't look as good as it could. But they will be used to that anyway. Plus higher end programs often provide tutorials etc that may be useful especially for the higher end functions.