I use a mAP that connect as a client to a Wireless network, then it share the connection by ethernet with a RB951.
The RB951 act as wifi AP and create a secondary separate wireless network with dhcp server.
I’m just looking to manage this with one device: can it be done with the RB962UiGS-5HacT2HnT or the RBD52G-5HacD2HnD-TC?
Sure.
You can use one radio as a client to existing wifi and the second for your own wifi network.
And more to it - this can be done even on the devices with only one radio, using virtual wlan interface.
The downsides of this approach are that both networks use the same channel and that the overall throughput will be lower, as you need twice the airtime of the radio to pass the traffic.