Apple Watch 4 gps and emergency sos calls

I currently have an Apple Watch Series 1. I would like to move up to a Series 4 GPS. My cell service is ATT Prepaid so unable to enable the Other Devices option on my iPhone 6s. nor buy/use the + Cellular Series 4. models

I know if the iPhone is within Bluetooth range I can press the side button on the Apple Watches (lets just talk Series 4) but if in another room more than Bluetooth will Emergency SOS work via just Wifi? On the current watch if I swipe down i see the Wifi icon illuminated. Looks like Series 4 does have a microphone so as long as its connected to wifi can I call my 911 service with only the watch nearby?