AP mode vs router mode

I work in a small office and a small warehouse near each other

We have 5g modem in the office That we connect to it with wifi , and I set one cable from the modem to a dlink access point in the warehouse that would convert from cable to wifi.

Everything was working ok except that the stupid Huawei modem does not have DHCP reservation feature that was nessesary to set a fixed ip for the IP cams.

Also the 5g modem offered very little control over my network so planed to buy an AP and give all local network control to it , so the 5g router will only act like a modem only, and hand all other work to the AP.

So I bought the archer C80 (supports DHCP reservation) and I connected the blue port to the 5g modem, and the warehouse cable to the yellow port, then I disabled DHCP on the Huawei modem and enabled it for the c80.

Everything seems to work fine except the c80 have very limited features( there is no option for bandwidth limit , VPN, disable ipv6) which is nice to have.

After some reading I found out that most features on the c80 are disabled because I enabled the AP mode instead of router mode.

As far as I can remember the internet was working in both modes without issues

My questions is: 1. Is it okay if I used router mode for my case ?

2.What is the exact difference between the 2 modes

1. Wich mode I should use ?

2. Is there is any 3rd party firmware for the archer c80 v1 that could give me even more control and features over my network?