The GPS in the 5DIV uses battery substantially faster than using the phone for GPS, especially when you just use BT (and not WiFi). The EOS R with BT and phone GPS is a great solution that I actually prefer, and they are slowly improving re-connect (e.g. when you fully turn the camera off for a while then back on, you need to launch the app the re-establish BT/GPS recording). It used to be after a couple minutes, now it seems to be much longer. It would be great if they could make it always just reconnect.That's my understanding of mode 1: the GPS unit continues to track location, even if the camera is switched off. Thus, when you switch on, the GPS unit does not have to re-acquire the satellites. Location data are recorded in images.
In mode 2, the GPS unit is off (so less power is used than for mode 1), but, when you switch on the camera, the GPS comes on as well and will re-acquire the satellite signal and, once acquired, will place location data into images from that point onwards.
If disabled, the GPS unit is inactive and no location data will be recorded.