In addition, you can fit in a manual save after fully defeating a wild Pokemon and the autosave doesn't trigger on faint/breakout/despawn, so you can essentially still take infinite retries if you so please despite the early fears about mandatory autosave.
On an unrelated note, I found a Shiny Alpha Staryu last night just returning to Zone 2 after night unlocked for the dex (taking my time through the game) and I'm glad I knew enough that it would both be stored and persisted even after being replaced by Magikarp in the night->day transition. I still ended up fighting it alive while trying to catch it the whole way through though, and Bayleef being able to take an Ice Beam from full HP was a fortunate breakpoint.
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The fastest friendship/happiness grind seems to be cafes giving a flat +30 happiness to the active mon (regardless of drink or current friendship level). I got a freshly caught Lopunny active in 6 drinks from basically base 0 to >160 happiness for the evolution threshold.
Bench hangouts also give +10 to the whole party, but you have to wait 10 seconds each time while you can just mash through the cafes regardless of time taken. Unlike PLA, getting EXP/breaking things doesn't affect happiness anymore.