Very nice work with the camera.
The Isolette III came with either the Apotar (a triplet) mated to a Pronto(r) shutter or the Solinar (a four-element Tessar-type) usually with a Compur.
The Apotar is a decent performer, but I've found that the 35mm version is sharper than the 120 version when shot wide open to about f/5.6.
The Solinar is a sharper lens.
The Isolette III was one of my first classic cameras, and once serviced it's reliable and a fun camera. The uncoupled rangefinder is easier to use than the uncoupled rangefinder on the Zeiss Ikon Mess Ikonta 524/16. However, the eyepiece is off center, so the closer you get to your subject, the more parallax becomes an issue.
As with all Agfa folding cameras, the trouble spots are the pinholes in the bellows (for those with plastic bellows) and hardened lubricant in the lens helical and also the rangefinder wheel. And with any leaf shutter, a routine service does wonders.
Overall, it's an attractive, pleasant camera with very solid construction.