The TPS demo (and more generally the Forward+ renderer) is high-end-oriented. I wouldn’t expect it to run with playable performance on a Pi 5. The Mobile renderer is expected to consistently perform better on low-end hardware, which includes all ARM SBCs that don’t make use of a dedicated GPU.
The Pi 5’s GPU in particular is very weak. To give an example, RPCS3 had to decrease rendering resolution to the PSP’s resolution (rather than the PS3) to achieve playable performance in its Linux ARM port.