Minimum width for a 2-paned window/patio door?

We have some floor-to-ceiling double casement windows that are only 1.20 wide.

We also use them in some places to get out on the terrace and balcony. With a breakfast tray in hand I can't get through the open sash ((

You have to wiggle out, turn around lengthwise. And when you are loaded for example with laundry, it is necessary to open both sashes. But this does not bother me in everyday use. We are quite thin, and when there is nothing in hand, we freely use only one open sash.

Our patio doors are 1.75m wide each. The bedroom windows on the second floor are the same. They are as you described, double-paned without a center bar.

All other windows and patio doors are "plain, as they are too narrow for two sashes."

We have two wings of about 80 cm each, and we only use one wing. However, we have house cats, so the door closes over and over again. But so far, all the people and items have fit nicely in the wing.

The patio door probably has to be double-leaf or it would be too heavy. For us, this applies to anything over 1m.

It's certainly possible. We were in Denmark recently, and there were some pretty narrow windows without an impost with two sashes that didn't look too bad. 

We have French doors (with triple glazing) measuring 2.34m by 1.17m. Consequently, you should also be able to use a single leaf element without problems with the weight of the element.

Based only on the width of the aisle, I would not take a patio door less than 80 cm wide.

We have two patio doors, each with two sashes and each two meters wide. Four meters of windows for eight meters of wall width – there's enough light coming in.

At the time, it was a relatively inexpensive solution compared to a sliding/lifting door.

We can live with it quite well, we can also exit through one wing at a time.

The wording means: looking back, I'm a little annoyed with my choice back then.

Today, I would design at least one of those two doors as a sliding/lifting door. Or full width glass with a sliding/lifting door.

I would also install a large window (floor to ceiling) and a smaller sliding/lifting door if needed.

At the time of planning, we had not yet developed living habits in the house.

We wanted to keep the ability to access the terrace left or right "on the cheap." In retrospect, it was unnecessary.... out of habit, we always use only one side.

The space required inside when opening the sashes is, in my opinion, a significant disadvantage (especially in a small house).

In the summer, when all the doors are open, the sashes must also be blocked by a limiter, otherwise they can open and close uncontrollably.