"And what if I created 2 dhcp servers (one for LAN (192.168.1.0/24 and one for Camera 192.168.9.0/24) on MX. Then I have to open a port for NVR on MX, right? "
you can create 2 dhcp servers without problem, you must create in the mx two vlan. if you like to open the nvr port to access from internet then you must open the port used by the nvr to internet.
if you like to open the nvr port to internet first you must configure the internet router from the provider in bridge mode to put the public ip address to the mx or configure it in dmz mode.
One little diagram to clarify a little the configuration:
Open the NVR Port on the firewall/Forwarding rules to internet
/
/ Configured as DMZ to redirect all ports to the mx
/ /
---- -------
| MX |----|router|
---- ------
/ \
/ \
vlan1 vlan2
(dchp1) (dchp2)