It's difficult to say as they're such different cameras.
AFAIK the FZ1000 has a fixed 24-200mm lens and is a 1" bridge camera whilst the G90 is an interchangeable lens MFT camera.
The G90 will presumably give you better image quality as it has a bigger sensor. However, the FZ1000 may offer good enough image quality in a versatile package, with that wide zoom range lens.
I have a Panasonic TZ100 which is a 1" camera and which there may give similar image quality to the FZ100. I also have MFT cameras. I can easily see the difference in image quality but 1" may be good enough for you especially if you can resist pixel peeping
I think you'll have do do some thinking. Do you ant a flexible do it all in one package camera with a fixed lens or one which may give better ultimate image quality but for which you may need to buy more than one lens for?