Catmandoo, the gradeability of electric power is phenominal. I'm currently (pun intended) driving a Mitsubishi Outlander plug in hybrid, and the power delivery to all four wheels is so controllable, with a motor at both front and rear axles, that a low range transfer case is not needed; in fact no transfer case is needed. Torque is there right from 1 rpm, so it will inch over obstacles with ease, and the regenerative braking is adjustable to a level that is nearly equivalent to using low/low on the downhills. The driveline is definitely off road capable, though the ground clearance and tires are not.
The present state of EV batteries has not overcome the effects of cold temps, my system lost about 25% efficiency when it got near freezing this past winter, but it was still more cost effective than operating a gas engine. The big drawbacks with EV are still range, charge time, and charging infrastructure. If you take your Rivian more than 1/2 its range beyond a charge point, you're not getting back home. That's why I chose a hybrid, with its own 2L high efficiency generator built in.