Is it better to plug in the RBS50 extenders

If "everything is working great", there is little to be gained by changing to wired connections.  For example, if the internet connection is running at 100mb, then having a backhaul many times that speed is already "overkill".

The benefits of separate wired connections to two satellites are pretty clear:

• The satellites do not have to share the 5G backhaul frequency  That 1333mb backhaul represents the maximum possible data rate, which is seldom achieved in practice.  My Orbi reports 5G transmit rate of 780mg and receive rate of 975mb to my single satellite.  WiFi uses bandwidth maintaining the connections, what with the radios sending out "Beacon" packets several times each second.  Your two satellites are sharing whatever bandwidth is achieved on that single 5G channel.  So, if your satellites are both connected with ethernet, each will have a 1G connection rate rather than the two of them sharing whatever rate they are able to achieve.
• Wiring satellites allows them to be placed farther apart.  As the distance between router and satellite increases, the maximum achievable data rate falls off.  The greatest possible backhaul rate is when they are very close together, but in that situation the two WiFi radios on the same channel create unacceptable interference.  As a general practice, "about 30 ft." is the distance where the backhaul rate is still "good enough" and the interference is "not too bad."

There certainly is no harm in experimenting.