I have 9 ft ceilings throughout my house. We have entry doors that are 6'8" with transoms. The windows are 6 ft tall but now that the house is framed I think that was a bit much but it was what the plans called for. All interior doors are standard 6'8" height. We haven't gotten that far in our build so I can't give an opinion on those but I think they'll look good as is. Here is a pic of the front of my house. The rough opening for the big double window in front is 6' x 6'. The window on the front porch on the same wall as the door is 3' x 6', those little openings on top and bottom are now filled in. That front door will have a transom.

Sorry, ronnatalie ~ I suppose I was thinking of American vs international plugs, which have (in assorted configurations) fat or slim round prongs or flat prongs or prongs of differing widths and in different combinations of round and/or flat, with 2 or 3 or 4 prongs per plug, set parallel or angled, centrally or off-center... and on and on. As long as the plug's prongs properly fit the outlet they were designed to fit in order to transmit the electricity for which they were designed, there really isn't any practical reason for using any one combination of prongs rather than another. No matter all the different appearances: each conducts the electricity to the appliance. The only consistency is that various countries have a preferred design. The preferred design is the local convention, and the convention is not due to practicality or a requirement of electrical transmission, but simply because sometime somewhere someone decided that only a particular design was to be used. Consistency does not have to have a practical or logical reason for existence; it simply has to be accepted by enough people for it to seem reasonable to be accepted. So whether it's about two-pronged plugs or in-swinging exterior doors, local convention rules local usage.

You certainly have room for 8' doors. Depending on the overall dimensions of the room, with 9'9" ceilings, 6'8" doors might look a bit skimpy. Traditionally, door and window heights are designed to be at the same level. It makes for a more unified and usually pleasing arrangement. If the guest room doors are sliders, you may want to match their height to the family room doors. If they are swinging doors, then a transom - even a narrow one - would be a lovely way to add height as long as the tops of the transom and the sliders match.

I spot your sister's trio of art next to your back door! They look fantastic there! (Did I suggest that? Or did I just think that was the right spot for them?) I still see Timothy's post. Maybe they vetted him and he proved he wasn't a spammer. That would be nice. We've had a rash of new posters who've come in and done nothing more than pitch a link on multiple threads. I reported on spammer who did that about a week back and the posts are now gone.