Its not really called for unless you plan to leave the car sitting for 6 weeks or more. Once the 12v is more than 3 years old it might be a better idea.
The 12v battery is very small but doesn't need more than a couple amps to boot the systems. But given the various issues involved with loss of the 12v power its smart to be aware. For example you really can't even access the 12v if you can't open the hatch.
Any type battery tender is fine, same as any other car.
If you can't reach the trunk and 12V battery you can still open the drivers door with the little key inside the fob, then open the door, then pull the handle that opens the hood. Inside the hood there is a fuse box with a jump starter connection. I assume putting a 12V source with a few amps maybe 5A capable is enough to get the hybrid system going. You could then open the hatch and replace the battery(or let the 12V battery charge from the hybrid system).
I'll be going away for about a month and live in Toronto, Canada, where the temperature will be around -10 to 5C when I'm away.
The RAV4H will be in a garage, should I just disconnect the negative terminal or is there's an easier way to help the 12V battery from going flat? Will audio settings, seat memory all disappear when the 12V battery is disconnected?
I have a Battery Tender Junior too and some smart plugs/outlet at home and can also set this up if it's better for the battery.