I do love old folders and use them regularly (just today I shot a couple of rolls with an Agfa Isolette III and a Mamiya Six). The Mamiya is, incidentally, one of the few folders that I know of with strap lugs. Some folders have a hand strap on one side, but most of them are designed to be used with the case.
I do not really fancy Zeiss glass on these folders, and I like the performance of Schneider-Kreuznach best. I have the Super Ikonta in 6x6 and 6x4.5 format and are great cameras, but for color work I'd never use them.
As others have mentioned, the choice of folders with lightmeter are pretty limited (I may add the Franka Solida IIL, I think it has not been mentioned). And chances are that it will not work (being exctintion meters, most of them do not have enough selenium left in the cells to provide an accurate reading, or even a reading at all). But dropping that requirement expands the possibilities.
Some top-of-the-range names I can't avoid mentioning are:
In 6x9:
- Bessa RF or Bessa II with 5-element Heliar lens
- Plaubel Makina IIIR, actually a press camera with interchangeable lenses and backs
- Balda Super Pontura (rare but worth it if you can find a good one, I have it with a Xenar lens)
- Ensign 8-20
In 6x6:
- Agfa Super Isolette
- Ensign 12-20 Special (uncoupled rangefinder, the coupled RF versions are rarer and always command higher prices)
- Mamiya Six with 4-elements D. Zuiko lens (not German, but one of the cameras I like best)
- Franka Solida IIIE with 3-elements S-K Radionar lens (probably the cheapest of them all, but I like it a lot, Radionar is one of my favorite triplets)
In 6x4.5:
- Ensign 16-20 (I have an AutoRange, coupled RF, and is great)
In addition, the Welta Weltur may qualify in any of the categories, since there were different versions made. I have the 6x4.5 one with Xenar, and is an excellent camera.
There are multiple other options out there equally capable (Perkeo IIE, Welta Weltax and Agfa Record III are some names that come to mind) but if I were to choose only one (which I can't), I'd start with the list above.