Is it possible to see the current voltage suppied on the port/ports? OR overall voltage being used by the router?
OK, so you are a pure IT guy with no electrician background.
Voltage (in Volts) is more or less constant unless you overload the source (adapter) and you can imagine it as a level of water in the dam relative to the height of the tap (or as a pressure in the pipe which is more or less proportional to the water level in the dam).
Current (in Amperes) you can imagine as water flow in cubic units per second.
The power (the input one in your case) is a product of the two. So if voltage is lower, the current has to be higher to deliver the same power.
In another words, what you ask for is to see the current current or current power, definitely not the current voltage. And I'm not aware whether the RB260GSP in particular can measure and display the current or power. But it if cannot, using an ampere-meter, an extra power cable and some cabling clamps you can measure the current taken by the RB260GSP with and without the device connected. However, the actual current may vary with time (the cameras may use infra-red illumination during the night) whereas the datasheets of the cameras should give you the maximum values.
With RB960PGS and a 48 V power supply, you should be on the safe side if your devices declare 802.3af support.
Instead of writing novels, post /export hide-sensitive. Use find&replace in your favourite text editor to systematically replace all occurrences of each public IP address potentially identifying you by a distinctive pattern such as my.public.ip.1.