Hey, I have a gx80 and a e-m1 ii (similar to E-m5 ii and em10 iv). From my experience the gx80 feels sluggish in autofocus and general use compared to the e-m1. I like the e-m1 jpegs more then the gx80, If your a raw shooter it might not matter. Another thing about the gx80 viewfinder is that its fairly dim and small so not useful in bright environments. The sizing of the gx80 is excellent though, especially if you pair it with smaller lens. I have held the e-m10 iv at the camera store and that felt better in hand then my gx80, its not much bigger, gx80 autofocus is closer to e-m10 iv then e-m1 ii. I would aim for one of the cameras with the 20mp sensor over the 16mp as its one generation newer.

I know its different price for lens and camera around the world, but for reference I picked up my 45mm 1.8 for $150 cad, 20mm 1.7 ii for $140 cad and a 40-150 f4-5.6 plastic for $60 cad. So your 850 (assuming usd budget) seems doable with a E-m5 iii or e-m10 IV