I went from a 5.7 Tundra to a 3.5 Tacoma. Here are some thoughts for you:
I tow a camper. We had a 28' beast of a camper that the Tundra towed effortlessly with a 10000 straightline WD hitch. Yhe 5.7 motor makes gobs of HP, but drinks a lot of gas to do it. The Tundra was comfortable, roomy and quiet in the cab. I found it to be a very capable truck for the 147k miles I put on it.
I traded it in for a smaller truck for a good amount of reasons. The number one being, we traded the camper in for a smaller model. The Tacoma's cabin is a little smaller, but not by too much. It's about the same size my 2000 Tundra was. I can actually reach the glove box now. The interior is comfortable, and the cab is OK for noise level. It tows the new camper very well using the same hitch.
As for gear hunting, yeah, it does it, but not when towing. You know why? Because I actually read the manual and know that you're supposed to tow in S-4, and not D on the automatic. The 3.5 creates its HP at high RPMs, and likes being there.
Other reasons for trading down:
The Tundra, while having an awesome turning radius (no joke) is a huge f***ing truck. I commute on rt 3, rt 4, sometimes 225, lots of backroads through Carlisle, Westford, Concord, etc, and it was really starting to be a pain in the ass on those narrow roads. The Tundra passed everything except the gas station. Over the course of 187 fuel ups, encompassing 54,606 miles (which was from the time I sold my commuter car until I traded the Tundra in), I averaged 14.9MPG. We bought a cap for the Tundra, and I couldn't see a damn thing once it was installed, but it came in handy.
The Tacoma is what I like to call my "mid-life" fun truck at this point. I'm having fun making it mine.
As for the 4.6 V8 - That's a hard pass. it is no more fuel efficient than the 5.7 in the real world, is under powered for the size of the tundra.
Here is some towing data for you with my Tacoma:
CoastieRon's Progression of Idiocy journal & BS
Of course, that post was before I put the small lift in my Taco. Feel free to read that whole thread, there's all kinds of great information in there.
Here is what my truck looks like now:
I'll be honest, the technology put into the 2018s is amazing. A lot of people don't like the Endtune suite head unit, but I don't use the Nav and Apps functions. Hell, I don't use the CD player either. I have gutted the speakers (there are 27-ish audio posts in that thread I linked), added some other stupid things that make me happy, etc. It's a great truck in my opinion, but opinions are subjective in nature.
I have always joined a forum for something that I own, or am on the path to buying. May I suggest joining Tundra Solutions or Tacoma World, and do some reading?