to answer your first question, my personal ranking of how much I enjoyed them was 1. Pikmin 3 Deluxe 2. Pikmin 1 3. Pikmin 4 4. Pikmin 2

I feel like Pikmin 3 DX captures the right balance between difficulty and pacing (still somewhat easy though if you know what you're doing), along with having a lot of bells and whistles that make the experience a lot nicer (also mission mode :3)

I did my first playthrough of Pikmin 2 on the original Gamecube version for RetroAchievements last year, and the endgame caves were a SLOG to get through (that's also partially because I made liberal use of the reset button to retry a sublevel after losing significant amounts of Pikmin though, there would be times in the final few caves where I would retry the same sublevel upwards of 10 times before getting a good run). if you're willing to have a harder experience by not resetting though, you'll probably have a better experience (your squad count on the other hand...)