AFAIK Hikey-960 HDMI peripheral Bridge IC (ADV7535) is limited to 1080p. You can explore existing boards here: https://www.96boards.org/products/. E.g. The Dragonboard 820c supports up to 4k60 FPS with h264/h265 hardware decoding. The Rock 960 seems to be a good candidate as well.
What kind of interface do you need to control your actuators (GPIO, I2C, PWM…) ? You have to take care about signaling level which is 1.8v on 96Boards boards, so addistional level shifter(s) can be requested.