Considering an HTT. Where do I start my research?

If you are camping when you need heated tanks and thermopane windows, a hybrid is probably not a great option. The tanks might be nice and warm, but the humans will be popsicles as all the heat escapes out the canvas ends.

That is, unless, you can stand/afford the furnace running constantly, which it will do to try and keep up with the heat loss.

For all intents and purposes the tents are the equivalent of leaving a door wide open regardless of how well everything else is insulated.