Having used several (Exakta, Exa, Nikon F, F2, Rolleiflex 3003, Praktina, various Practikas... - just as far as 35mm is concerned), I'd say that the best quality is the Exa/Exakta (at least with the older magnifyinging/condenser WLFs), while the most convenient is the Rolleiflex SL 2000 / 3003 (switchable between WLF and eye level finder in a fraction of a second).
As mentioned, most of the Exakta's will take a waist level finder. I have both the WLF & pentaprism for mine. Exakta V & VX in my case. They have the flip up magnifier so focusing is easy. It's kind of a backward camera because the wind is on the left side.
There were Rollei and Yashica TLRs with 35mm adapters. These were OK for vertical composition but awkward for horizontal composition. Both had waist level finders standard. There are 35mm backs for the Bronica ETR and SQ series cameras. I have the 35W back for the ETR cameras. It has the same 24X56 image area as the W back for the SQ cameras. I read somewhere that there was a prototype 35mm back for the GS-1 but that the camera went out of production before it could be manufactured. Some people have rigged up adapters which look like Rolliekins for other medium format and large format cameras.