QIf I use this follower's Fanfare ability to summon two iM@S CG followers with Fanfare abilities, in what order do each follower's Fanfare ability and this follower's non-Fanfare ability resolve?

AWhen multiple followers with Fanfare abilities are summoned with the same ability, you can resolve their triggered Fanfare abilities in any order.

QCan I choose to only summon one follower with this follower's Fanfare ability?

AYes, you can.

QIf two iM@S CG followers are put onto the field at the same time, will this follower's non-Fanfare ability trigger twice?

AYes, it will.