I've read on the Samsung subreddit that some apps may be linked to this. Dunkin donuts' app was mentioned.
I uninstalled it and everything worked. When I reinstalled it, all the problems returned.
Mine was reproducing consistently. I tested on two different networks, one was a fiber connection. For my phone, it was clear as day that turning the blue tooth on was killing the wifi.
I'm sad to say that a factory reset did the trick for me. I guess that's good news since it means it's a software issue. It's just total BS that you have to factory reset a brand new flagship phone to get it to work right.
Having the same problem with a Verizon S7 Edge. Speedtest with BT off was 10 mb/s down. Turned bluetooth on and ran it a second time and it dropped to to 100 kb/s.