I'm trying to answer that question right now and have read every review or comparison of either I can find on this sub. Here is my take:
It is entirely up to your personal preference and situation.
For all major features, both are equally functional. Both have demos, so use both of them and find out. Tandoor's UI felt more clunky to me, and I can't get it to display a recipe with ingredients on a single screen, so I'm going with Mealie. Other people like Tandoor's more granular ingredients/instruction organization.
None.
It's exceedingly unlikely that ANY general-use network OS will recognize or even run on it. Even if it did, as it lacks actual switching hardware, it would make a very poor switch.
As for "change its ... VLAN [configuration] with a simple click" that's almost certainly an XY problem.