I just got back from Japan, two days ago.
I was in Tokyo. The best place to find a variety of Tamagotchis there is the TamaDepa (Tama Department Store) at Tokyo Dome. There's a balcony going around the outside of Tokyo Dome. The TamaDepa entrance opens onto this balcony. The easiest way to get to it, is to go up the stairs to the balcony, just to the right of Gate 22 (as you're facing the gate from the outside.) You don't need to go through Gate 22. There's a small map on their official site:
https://link.channel.or.jp/tamadepa/ You should be able to find Royal FamiTama, regular FamiTama, TamaSuku, EnTama CYOI, and ChibiTama there. Other than in TamaDepa, you'll not likely find so many different models.
Most large toy stores should have the Royal FamiTama. A few might have some of the regular FamiTama left. A few might have some TamaSuku or TamaSuku 2 left. A few might have some Tamago-chu left.
Here's a summary of what each model is like.
ChibiTamagotchi = same as Tamagotchi Mini
EnTama = similar to Connection V4
TamaSuku (Tama School) = nothing like it was never released outside of Japan. There's an excellent English-language guide here:
https://www.mimitchi.com/tamasuku/index.shtml
Tamago-chu = nothing like it was ever released outside of Japan. They come in a box of two. There are photos and a description on this site:
https://www.tamenagerie.com/Tamagochu.html
The FamiTama = Connection V5 / Familitchi.
The Royal FamiTama = nothing ... yet. It seems the Connection V5.5 will be similar to the Royal FamiTama.
Another source you might want to try is auctions.yahoo.co.jp - it's the Japanese equvialent of ebay. If you're staying with relatives or friends, find an auction set to close a few days before you arrive. Get your relative or friend to bid on it, and if they win, have it delivered to their home. Then you can pay them when you arrive. Here's a link to a category with Tamagotchis in it:
https://list4.auctions.yahoo.co.jp/jp/20840...ids&o1=a&mode=2 You'll probably not find any fake Tamagotchis in there, but you might find some non-Bandai virtual pets.
As to which model should you get? ... If you don't have any Japanese Tamagotchis right now, I would recommend the Royal FamiTama. I suspect it will be able to connect to the Connection V5.5 (when it comes out) and if it does, you might be able to get a special baby by mating them together. If you have an EnTama or UraTama already, maybe get a TamaSuku - you can connect them.