1 camera, 1~2 lenses, cables, small accessories; for example, Sony A7 kit (24-70mm), Sony A6400 kit (18-135mm), Nikon Z50 kit (16-50mm f/3.5-6.3, 50-250mm f/4.5-6.3), Fujifilm X-A7 kit (15-45mm), Fujifilm X-T20 kit (XC 15-45mm), Canon EOS M200 kit (EF-M 15-45mm), Canon EOS R5 kit (RF 100-500mm); power bank, ipad mini, data cable, mobile phone, etc. Lens that can be installed: diameter ≤12cm, height ≤26cm 

This multi-functional fill light & mobile power supply is a 2-in-1 style that can charge any device 

1080P @30FPS 

Take a power bank and charge that with the panel and then charge your GoPro. Faster and less expensive if anything goes wrong. 

Yes, when you use one camera alone, just shorten the other side and fix it under the armpit, then you will have a double shoulder strap.