To have a “real” bridge (L2) the two devices connected need to exchange a certain number of parameters, start reading here:
If we call AP the device that Is connected directly or indirectly to the internet and allows wifi connection the other device that connects to It, like a phone or tablet, or your AC lite, Is a client (also called station).
Mikrotik devices have a station mode called station-bridge that if the AP Is also Mikrotik allows L2 bridging (using proprietary, non standard, method) but if the AP Is not Mikrotik doesn’t allows It , like the “normal” station mode.
To give you an example of a station mode, It Is what you would use on a Mikrotik device like - say - a mAP to add wireless connectivity to a single device that only has an ethernet port (say an old PC).
See:
Mikrotik has this mode station-pseudobridge that some people call L2.5 as It offers something midway between L2 and L3.
Then you have “normal” L3 connectivity (routing) that implies that there will be double NAT (one on your main router and one on the station device). Notwithstanding the common opinion that double NAT Is bad, in practice for normal internet use It Is irrelevant or not noticeable ( while since It increases latency Is a no-no for gaming).
The other option, the tunnel, Is more complex to implement and requires some adding computing load, so It Is not advised on low power devices (such as the AC lite) as It may slow noticeably the connection speed ( and It has to be seen in you case what your Netgear supports).
Easiest would be to procure another Mikrotik device, but this should be using the same set of drivers (to simplify, there are two sets of drivers, the “old” ones set under “wireless” and the “new” ones set under “wifi”).
Some Mikrotik devices can run only the old ones, some only the new ones, and some both (It depends on RoS version running and on architecture/processor of hardware).
If you decide to buy another Mikrotik device ask for advice in choosing which device would be suitable before buying It.