Speaking only to tandems, as it's far different once you include the rest of the bikes in our stable....
Drive Chains:
Speeds: 9 & 10
Brand/model preference: Shimano XT / XTR of late, various different SRAM
Typical mileage (metric or miles OK): Varies quite a bit depending on terrain. Let's say 2k for road, a few hundred for off-road noting that I usually change when wear approaches 75% on a Park CC: I much rather chuck off $25 chains vs. $100 cassettes & $20 - $45 chain rings.
Road or off-road use See above.
Tires
700c or 26": 700 = road, 26" = off-road
Primary function: Recreational road & off-road
Team + bike weight bracket: Light
Typical mileage: Tandem-only, 3,500 yr is probably a good guess.
Brand/model preference/width: 700 = Vredestein Fortezza @ 23mm, 26" varies with terrain / soil conditions.
Good luck trying to analyze the data. Frankly, it's analogous to figuring out why men prefer... (and what a list that would be).