Whatchou takkin 'bout? Is this an instance of quantity disagreement?

I already have two computers mounted to two bikes, inherited from their previous owners, and a wireless computer currently waiting to be mounted. The wireless is a Cateye strada and I'm not sure if I can easily track multiple diameter wheels with it. I recently bought a 4th bike, with no computer, and I'm debating if I should revamp the current setup, or keep the basic information on the handlebars while tracking other metrics like cadence, elevation, etc. with my phone in the pocket, and adding a HR smartwatch sometime later. I think the proposed setup provides the most flexibility and value because the smartwatch is useful for tracking other exercise off the bike.
I can do all of this for about the cost of a Garmin head unit before multiple mounts and sensors.