Have you tried the Nikon Z's, they were much better imo and I could easily hold the camera in one hand with the 24-70mm f4 attached, for how long though I'm not sure. My EM1-II and 12-40mm f2.8 is a doddle to use one handed, but even with this I'm not sure I'd want to hold it for extended periods, I'd end up with cramp
I find the peak design slide invaluable, means the camera's there whenever I need it , but I can also be hands free without the camera swinging about like it does on the BR straps.
Depends on the combo, as mentioned above