Hi @p-uchi , you should also consider the VPU encoding capabilities, which seems to ve be limited to 1080p60 in the i.MX8MP. Otherwise you will have to use SW accelaration which could be very very slow / 100% CPU usage.
I see some users commenting in NXP forum about encoding 4K with i.MX8MP and NXP discouraging this because of limitations of the SW control:
We recently added VPU support in Torizon, so let us know if you need more help on this.
A single 4k camera seems to be too much. Dual then… 
Kind regards,
Alvaro.