>>95942261 (OP)As the other anon said, all of those are valid.
There are no shoulds here, it'll certainly depend on a lot, including the system.
For example, in this D&D 3.5e campaign I'm playing, the technomage sometimes summons a bunch of robots, and that grinds the combat to a halt when he does due to all the extra resolutions steps needed and stuff to keep track of.
In turn, my Cleric has a Celestial Raven companion, and I seldom ever even mention the critter or use it in combat, even if the character has maneuvers where he does shit in tandem with the bird, and when I do, the DM just handwaves the initiative and stuff since the bird doesn't participate in combat besides moving and being part of those maneuvers, and even that adds a tiny bit of overhead to my rounds.