If you get the car into the point where it will turn on the REx in the way it is configured in NA, you must understand that while the REx engine can produce enough energy to keep you moving at reasonable speeds, it is essentially just a 34Hp engine. When was the last time you drove a car with 34Hp? Plus, whatever the SOC is when you shut off the car, that's the maximum it will try to attain with the REx, so if you just were pushing it, and the charge got lower, that's the new max. If you're not careful, you'll essentially be stuck with a 34Hp car since there won't be anything left in the battery to act as a buffer. If you understand this, yes, you can drive the car as long as you keep filling the fuel tank, but you'll have max performance if you charge the battery up again. As sold elsewhere, you can turn the REx on with a 75% SOC, and thus preserve full capacity unless you want to drive with a full load, lights, heat, uphill at high speeds, then you'll be drawing down the battery. If you don't get it too low, it will recover some going down the next hill, but could get low enough to cause the car to slow down. Max continuous, flat road speed and being able to maintain charge seems to be about 70mph...faster, and you'll be depleting the batteries.
While some people use the i3 with REx for long trips (and it will work if you understand its limitations), the car was designed for short distances with the REx as an emergency backup, otherwise, they would have put in a larger engine so it could maintain performance forever. Many people buy the REx version and never use it except to test it. If you need it, fine, but it does add to the cost, complexity, and maintenance costs since you now have a muffler, oil, filter, spark plugs, etc., associated with the ICE. The REx is also less less efficient than the BEV, partly because of the extra weight, but also because it doesn't have the heat pump the BEV can, which means any heating is a 1:1 ratio from the battery:heat, whereas on the BEV, most heat is about a 3:1 heat: power use.