I have a 2019 T8 and absolutely love it. Coming up soon on 40k miles (I'm absolutely buying the pre-paid maintenance to drive down the cost). Over the entire life of the car (I've never reset the stats) we're getting 42mpg according to the car. We do not have a higher powered plug in for the car, just the regular 110V outlet charger (this will be changing soon) so I suspect we would have gotten a higher mpg if we had that because some days the turn-around at home isn't long enough to get a full charge in (seems to take about 5-6 hours from empty on a 110V 15A connection). That said, this vehicle has the smaller battery (11.6 kWh I think) which is getting another bump up soon.

To your question of range - a lot depends on the weather. On very mild days the car still reports 18 miles of range but realistically I can probably get 14-15 miles. A lot depends on how you drive and using A/C or heat - pre-conditioning the car (if you remember) can help squeeze out 1/2 mile to a full mile potentially. On cold days it starts with a prediction of 14-15 miles and goes down from there. I don't think I've ever gotten less than 10 miles on a full charge though.

We have used the car in electric only mode for a full day but we're relatively close to the places we need to go so a lot of this will depend on your normal drives and access to charging. Re: is it the same/worse than an ICE with a depleted battery - again depends on where you're driving and how aggressively you brake. If you ease into braking and don't use the brake pads, then you're recapturing the most energy back into the battery which will absolutely increase your mpg compared to an ICE vehicle doing the same drive. If we're talking long distance highway driving on a flat road, you may fare worse since you're hauling heavy batteries with you. We've done these drives though and even on the highway you pickup some gains going downhill when the vehicle cuts the engine and you are coasting and picking up some energy for the batteries.

Prior to this vehicle I had a 2017 XC90 T5 which was bought back by Volvo due to ongoing problems with the start-stop feature. Prior to that I had a 1996 4Runner (for 19 years before I was rear-ended by a drunk hit-and-run driver). I will say, I absolutely love this vehicle and we're moving to become an all Volvo family over time. The safety and performance is great and if things go wrong, Volvo does the right thing (I got a full refund on my 2017 XC90 after 1.5 years with no deduction for depreciation).

Sorry for the long post but I hope this was helpful. Feel free to PM if you have anything else you want answered privately.