Window with transom or without? Transom with tilt sash or fixed?

And a large window without a top light (tilt-and-turn) no alternative?

Yes, of course.

Or does it just not look aesthetically good?

Well, these are no windows with curves or frills.
I assume it was more practical back then for permanent ventilation. There was no need to save. The benefit of short cross-ventilation has only been known since the internet existed ;) And permanent ventilation is something you possibly want to prevent when renting out (heated).

I would give you the "Go" for a sash unit if you are waiting for it :)

We don’t have an energy consultant

Now, interior insulation was installed afterwards between a double wall.

You mean a stud frame / battens / spacers were installed from the inside and filled with mineral wool in between, and then gypsum boards were placed in front? That can be done, but it’s physically difficult and prone to errors. But since it’s already installed, in any case seal all penetrations and connections airtight and vapor retardant. Above all, use only airtight sockets suitable for these spots and don’t just plug and screw them in, but additionally seal the support with acrylic/sealant. Seal all edges at the top and bottom through the hopefully inserted vapor barrier with suitable sealing tape (not just baseboards). Interior insulation based on mineral wool with drywall is feasible but can backfire if too much room air and thus moisture get behind it.

And a large window without a transom window (tilt and turn) no alternative? Or does it just not look good aesthetically?

I think, at the moment with the transom window and white plastic, it looks like a ‘60s building – a classroom or government office. I’m a fan of muntins. Simply windows without divisions always look like black holes from the outside. I would use one sash but loosen it up with muntins applied inside and outside or glass-dividing muntins (NO muntins in the glass spacer – disgusting). Size-wise, muntins shaped like a "T" could fit without looking overcrowded. Overall, it’s cheaper than a transom with a sash and easier to clean since you can open the whole sash inward.

Edit: Just checked the dimensions again. With those sizes, you could also simply use double sashes with a mullion. That also looks nicer than a large one, and the sashes are narrow → the fittings are less stressed.

And I would think completely anew, possibly a fixed parapet element at the bottom and then a window sash in the upper third. This has the charming advantage that window decorations for ventilation can generally remain in place. In addition, the parapet height does not appear so high, so for kitchen planning such a window can also have positive effects because a worktop can also be led into the window reveal against the glazing frame, resulting in at least 6 cm more working height.

Our window niches are 160 cm high, the lower glazing frame is about 7 cm, the bottom edge of the window sash is 48 cm above the windowsill.
The single-sash windows are about 95 cm wide and separated in the upper area with applied muntins. The window niches of the double-sash windows are just under 150 cm wide.

From the outside, it can then look like this:


The window cleaning problem is thus also solved.

I agree with @till ... it could also be double-winged windows in the upper area.