Yep, daughter's hardtail, son's AM /trail bike, my Soul hardtail do it all refined hooligan bike, and my more money than ability carbon AM bike. See
@GrumpyGregry 's post about what old men with too much money need in terms of bikes. I don't have a singlespeed!
As for chain tensioners? Well, double ring setups need a bit of help to calm the chain down on the clattery stuff. A lower mounted chainguide (not necessarily a tensioner) does two thngs in the case of the Hardtail, and or four things on the bouncers. . Firstly, the roller mounted behind the chainset ensures that the chain leaves the chainring in a straight line, hence the term "guide". The red one on the Soul is a Blackspire Stinger, and has a polymer stepped roller. On the big ring the chain sits deep into the roller which is sort of diabolo in profile. It's fitted so that the chain is almost pinched and so leaves the chainring in a dead straight line. It only changes direction after it leaves the roller, so any lateral movement cannot dislodge the chain from underneath the chainring. The pinch effect also pretensions the rear mech, and so has a damping effect on chainslap, preventing damage to the chainstay, especially on rough descents when you're pedaling in the big ring. On the Soul the front mech is set so as to prevent the chain shipping outwards from the top of the chainring. I also have a Deda Dog Fang which prevents the chain shipping inboard onto the BB shell from the granny ring. The 2x9 setup on the Soul is an XT triple, with the outer ring replaced with an alloy bashguard which prevents damage to the big ring's teeth, and stops the chainring eating your leg if you come off. The 32 T middle ring was replaced with a 36T ring to give me taller gearing.
The devices on the Canyonstein and the Mojo are MRP 2x systems. The chainsets on those are XT double specifics, with 38T outer and 24T inners. The devices have jockey wheel rollers instead of the polymer roller on the blackspire, but the guiding/retention principles are the same. Again, double specific front mechs are fitted as close to the top of the chainring as possible to retain the chain at the top. You can't fit an outer bashring to an XT double, but the MRPs have an integrated skidplate bashguard which you can see on the photos protruding between 3 o'clock and six o'clock on the chainset. This stops logs, rocks and steps from taking the teeth off the chainring. To prevent the chainset biting your leg you learn to shift into the big ring for descents. Finally, the mounting plate of the device has a raised fin which sits close to the chain when you're on the granny ring, and this stops it shifting off onto the BB shell.