From what I understand, InnoDB is superior in most ways.  It has row level locking, where MyISAM only has table level locking, it self repairs by comparing itself to older versions of itself, where MyISAM does not, and it's generally quicker because of some feature of its indexing that I can't recall.  I probably shouldn't bother listing what a simple google search can provide a much more detailed and technically articulate overview of.  Anyway, just throwing it out there.

Yep. Invision Community uses whatever your MySQL server's default type is set to, which should probably be InnoDB.

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MyISAM is based on the older (and no longer available) ISAM storage engine but has many useful extensions.

https://dev.mysql.com/doc/refman/8.0/en/myisam-storage-engine.html

It will take years before they completely phase out MyISAM but the plans are in the works.