I considered this, but I'm pretty sure save files on the Switch are tied to the account, so If I wanted to switch (HAHA!) back to my NA account, I don't think I could keep the save file, even if it would let me play the game in English.
Very unlikely. If it's anything like the Monster Hunter games before, than the Japanese version and the "not-japanese" version will be like 2 separate games - mostly due to licensing like special branded items.
Improved resolution and shadows are all I notice.
There is also a visible bump in poly count (noticeable in the screenshot with the ship)
Always looked bad in screens but when played on the 3DS it looks quite solid imo. Still the difference to the Switch version will be massive thanks to the resolution.
sometimes I wonder if people who refer to screenshots when talking about the 3ds monster hunter games actually played them... because in motion on the screen they don't look anywhere near as bad. The game's style, and the 3ds in general, just doesn't lend itself to pics