One SSID for all devices (if so just use same ssid and password on all devices and most clients will hop between devices without problems, there is more options like 802.11v, 802.11k, 802.11r but they are not necessary)
One device with wired connection and others work as extenders (if this more info bellow)
Currently there is no good way to use both bands because regular 802.11s meshes do not have loop avoidance also because of this only use wired connection on one device
Bands:
2.4ghz - better penetration, more congested, lower speed
5ghz - worse penetration, less congested, higher speed
Frequency/Channel
2.4ghz - use Status > Wireless > Channel Analysis and pick least used one or any of them if you are in less congested place
5ghz - same as 2.4ghz but also would not recommend DFS channels
I forgot to mention that I want to connect each node (TAP 200) via cable to a PoE switch, which in turn is connected to the RUTX50 via cable.
I think that since the TAP200 are already connected via cable, 802.11s (Mesh) is unnecessary.
Would 802.11k & 802.11r then be the optimal solution to enable fast and seamless roaming between the access points?
When you have multiple devices with same SSIDs these additional options can help but they are not necessary. You can enable 802.11v and 802.11k but 802.11r requires bit harder setup then it is worth for regular network