Considering an HTT. Where do I start my research?

My personal opinion is that I would not worry one bit about the heated holding tanks or thermopane windows in a hybrid.

I had both in my toy hauler and I did like the windows but the holding tanks were never on. In my new hybrid I skipped both. There will be so much transfer in the canvas ends that the thermopane windows are sort of pointless.

Just my two cents. That 23IKSS is awesome! I went with the 21DK because I really wanted to keep the length short but I absolutely love that IKSS floorplan.