Tim, mine was the 94kW, (I did run an earlier one with 60kW as well)

The 94kW Rex would do around 120 miles on pure EV, & yes you could run 'unlimited range' by just topping up the petrol for the Rex generator, we've done London & back sometimes without plugging in

When BMW dropped the Rex in the UK they bunged some extra batteries in the Rex space increasing to just over 120kW, the published range was I think 193 miles

Jon M