api3/4 difference: you can no longer use names instead of ids
As I understand it, in API4 you can no longer pass a name where you 'should' pass an id.
'option_group_id' => 'activity_type' will no longer work. Instead you should do something like
\Civi\Api4\OptionValue::get() ->addWhere('option_group.name', '=', 'activity_type') ->execute()
Seems like this would be useful to cover here https://docs.civicrm.org/dev/en/latest/api/v4/differences-with-v3/ but wanted to run past someone like @colemanw before doing so.