Hey @mit,
You’ve brought up the better points between BSP 5 and 6. BSP 5 is still a LTS release, and is used on new builds specifically for cases such as this where support is more defined. BSP 6 and this model should eventually gain support, but I don’t think anyone could give a date on this. If FreeRTOS is a larger driving factor, I would say BSP 5 is the correct way to go.
On Zephyr, you may find similar requirements for setup are needed, Toradex doesn’t test/validate. But we do contribute to the Zephry community… For Colibri IMX7 see:
https://docs.zephyrproject.org/latest/boards/toradex/colibri_imx7d/doc/index.html
From this I would lean towards BSP 5 + FreeRTOS. (as my personal advice)
-Eric