I have a love/hate relationship with RTTs. While they provide a nice place for sleeping, they displace what I consider a great place for carrying/storing things. I'm not a fan of open racks so both of my rigs have Packasport storage pods and I love them. They're quiet, aerodynamic and forces me to keep things light and low profile. However, when the RTT goes on the 80, I lose all that storage space and because there are two medium size dogs in the cargo area, not much can be stored there either! Furthermore, my Columbus RTT changed the COG enough to be quite noticeable on the off camber stuff. I'm thinking of lowering the 80 to 3" and switching to 255 85 16s from 315 75 16s.
Sounds like you can get away with a RTT since you have a tiny dog so your cargo space can be utilized as true storage. If you get a SUV, removal of the second row seats will yield more storage. An exploration rig needs to have a decent boxed chassis for longevity so make sure you pick an appropriate platform. I think you're in the fun stage of your journey, trying to come up with the ultimate platform while minimizing the compromises.
I LOVE my 4th Gen and how it tows the Kamparoo. This is a low profile rig that is very efficient and easy to drive. That V8 is work of art and so tight. At 325xxx miles, I have zero leaks. Given that it won't see severe rock crawling in its future I'll set it up mildly while keeping the added weight to a min. I think it has more useful volume inside than my 80 but I love them both for their own attributes.
Ergonomics is very important so try out different rigs to see which one fits your frame nicely. On long trips, arriving at the destination well rested is a priority for me. Some of my friends arrive at the destination beat to hell with a minor hearing loss! Ok, I exaggerate but NVH should be a strong priority IMHO. The landcruiser allows me to sit upright and tall like a dining room chair vs the 4runner, which is a tad lower with my legs out front. I wasn't sure if my lower back would like the 4Runner seating style but so far so good, additionally, it's a quiet platform and it doesn't beat me up on long trips.
Good luck with your mission and PM me if you have any questions.