Are Cleats Necessary with Vector 3 Pedals?

I ride a bicycle as an enjoyable method of getting meaningful exercise I no longer get as a retiree. Every couple of days I ride and my idea of a physically worthwhile and enjoyable ride, at this point in time, is to maintain an average speed of a bit over 10 MPH for about 10 miles. I am currently gradually increasing that distance and probably will settle at 15 mile, 1.5 hour rides. I am certainly not into racing or endurance and have zero desire to get every bit of performance out of myself and the bicycle. That being said, I like my toys and am currently considering buying a pair of Garmin Vector 3s pedals. My reason for buying them is primarily to satisfy the geek part of my personality and see accurate data on the energy I am instantaneously expending and how that integrates into total calories burned over the course of the ride. These will replace the Garmin cadence sensor I now use with my Garmin 820.

Now my question. I almost pulled the trigger and bought these expensive toys but luckily noticed on YouTube riders using the Vector 3 pedals had orange or black cleats attached to their shoes. Needing to gear up by attaching cleats to my shoes is a bridge too far for my needs which is only to see as accurate energy data as reasonably possible. My idea of preparing for a ride is firmly limited to just getting a cold bottle of water, opening the garage door, mounting the bicycle, and then just start pedaling.

So, please tell me why the cleats are needed or really not needed. $1K is a lot to spend if the data will not be consequentially more accurate than I see now or the pedals will become uncomfortable to use without cleats.

How do the cleats mount to ones shoes and are special shoes needed?

Thanks