I really like the PL100-400 on the G7. The combined lens and body weight is well below 2kg, so this can come with me every time I'm birding, regardless of whether I'm carrying my scope and tripod too. I'm a birder who travels by bike and so the weight and bulk of my dslr and 200-500 results in a choice between scope and camera and the scope usually wins. I'll likely use that gear in future only when I know I'm setting out to take flight shots of some small and/or fast beastie.
I've found the 100-400 to be excellent wide open and through the zoom range. Pixel peepers will probably find fault, but that's not my territory, and as a birder wanting better than a bridge camera can deliver this m43 camera & lens will siut my purposes well, I think. The PL100-400 is seriously better in all respects compared to the lumix 100-300.
Video/vidgrabs are also much better with G7/100-400 compared to my previous GH3/100-300. The 2.4 internal teleconverter works with full hd video, giving serious 'birding range' reach, and the fullhd grabs are decent quality.4k obviously better, but added teleconverter range is not available. Decent lens for plants and butterflies too.
Sunbathing dunnock from 10m, little egret and herring gull both big crops from 120m, juv robin vidgrab from 25m (full hd @800m equivalent,+2.4 teleconverter.