I would like to shed a perspective related towards the "gasser" helicopter.
TT (Torque Tube) has less friction & resistance than a belt drive system. This is very negligible whilst been driven by the power plant, however when auto rotating, there is a difference that can be noted. The shaft (TT) is held in place & driven by many more bearings than found in the belt drive system which has more resistance at the belt & pulley contacts. For this reason the TT system therefore has slightly more hang time in the air than a belt drive system, but not to the degree that makes a belt drive system unsafe or obsolete.
The Morphis has two tail belt drive gear options - Plastic & Aluminum. A rotating mass does not really consume or dissipate energy. A rotating mass stores energy. You will find using the heavier Aluminum Xl gear that Autos will be comparible to that of a TT tail drive system. Even with the heavier XL gear the overall tail drive system mass is still lower than the Align TT drive.
The gasser is however subject to more vibration & harmonic frequencies than an electric or Nitro machine. Vibration & harmonic frequency has very little impact on a belt life but its impact is influential on bearing & gear life & needs to be monitored.
The TT introduces on average eight more bearings within the tail drive system that are usually hidden, hard to get to & are more fragile in nature due to size, however this is what accounts for the additional extra hang time in an auto.
A well designed belt system will usually only have two or three additional bearings within the tail drive. These are located within the pulley guides, & are located externally which makes for effortless inspection, lubrication & if needed replacement.
Both systems have their merits & both will work in the gasser environment. The belt system has less maintenance & is also less prone to bearing & gear failure in a gasser making it more dependable especially if used commercially. The TT drive offers less resistance in autos which results in slightly more hang time in the air but also provides additional maintenance (strip down of tail drive for periodic bearing inspection) & an additional bridge for resonance to travel within the system, while a belt can actually create its own resonance frequency (but at our scale it is not a dominant issue) & a thicker boom or additional bracing required to compensate.
It is important to keep a flight log & to record failures so you can develop a maintenance schedule for components & an overall picture of advantages & disadvantages of certain systems & components. What I have found is that in a "gasser environment" bearings tend to have an earlier life cycle & the size of bearings in the TT system are hard to source in hybrid ceramic silicon nitride bearings not to mention costly.
If I was purely flying electric my preference would be TT over belt. In a gasser it is leaning towards a well designed belt drive system. So I would question the 50 second youtube proof that TT is superior. It depends on application over data collected in field application (not a stationary test) is the correct answer to this debate.
In a gasser application my opinion would change to dedicated TT if a more affordable Rotary Wankel engine was available.
To date the few developers that actually produce & sell these engines are specific for long range drone applications & well out of reach for many with a price range of $6000-$18000 USD. The exception is Nitto ($1450 USD) & Thunder Tiger may also be producing a 50cc gasoline Rotary, a prototype was released but getting information from them is proving quite difficult. Torque & power curves of a rotary wankel (the little information that can be obtained) is also questionable. A viable economical solution at reducing engine vibration & gaining additional power is being worked on. A new engine in evaluation has now been purchased. Airframe design & testing has begun. The Key to reducing vibration levels in our application is torque/power/gearing at specific RPM without the need of blueprinting.