Despite this board being dead, i'm in the mood to vent about my current playthrough, so i'm answering this anyway.
>-Is the gameplay engaging and challenging?
Pretty even. I often do quests or grind for plans in between multiple cutscenes.
>-Are there branching endings and other things I need a guide for?
There's a share mechanic that you need to manipulate for some resources can lead to two different endings afaik.
>-Is the gameplay engaging and challenging?
It's so so. Combat can be tactical and positioning is very important, still most of it boils down to spamming attacks on tanky bosses.
>-How much fanservice is there? (Asking from pro-fanservice angle)
What you see is what you get. The designs are sexy and there is lots of innuendo, no out there CGs as of yet.
>-Does it really have "fourth-wall-breaking, trope-demolishing dialogue" as the Steam description says? (Asking from angle where I would find that potentially cringe)
I'd say it's more chuuni than 4th wall breaking. It's self-deprecating cringe.
>-Is the experience gimped by not getting certain game industry references, etc etc?
Sometimes, but how could you not know petit charat from the hit franchise digi charat?
I'm at the fourth chapter and while determined to finish the game, the experience is starting to wear down a little. Reusing the same mountain and factory environment has become nauseating and enemies are just to damn big, i can barely maneuver around them. The story is still cute though.