Concerning “tether angle losses” I do not see other losses than cosine cubed losses.
That said TRPT (including Tiira) geometries involve limits of torque transfer. They are summarized for Daisy (ground rotor parallel to the flying rotor, rigid transmission rings), for Rotating Reel, see figure 22.18 (ground rotor non-parallel to flying rotor, no rigid parts in the TRPT, little potential for height compared to the diameter of the ground station), see the calculations for The Pyramid - Engineering / System Design - AWESystems Forum, click on ‘here’ for the pdf.
Calculations are complex, but to summarize, the axial force (tension ensured by the TRPT and the lifter kite if applicable) must be high enough to allow the torque transfer in optimal conditions for a correct (?) but necessarily limited height.
Concerning TRPT including Tiira (no rigid parts in the TRPT), one of the parameters is the diameter of the rotating ground station, leading to the usable length of the two respective tethers of the two kites.