There was a question about charging during storage. You’re not supposed to. They don’t discharge nearly as quickly as lead acid batteries, and the recommendations I’ve read say to just store them at 50-75% and forget about them until spring. Not sure about storing in sub-freezing temps.
You can add Bluetooth monitoring to any battery for $40, which I have enjoyed having. Link to Amazon: https://a.co/d/43uYpDh
The battery heaters are just small 12v silicone heating mats. Search them on Amazon. You can install them on a switch with or without a thermostat. I convinced myself this would be the solution if I needed it, but I haven’t needed it. I’m also pretty sure I could run my batteries for 2-3 full days before they’d go dead (36v system). They have sooo much more juice than my old Optima Blue Tops.