Need some advice on using some legacy Orbi systems - RBR40, RBS20, RBR50, and RBS50

I am looking for some advice on how best to proceed (sorry for the long description).  I manage the IT at our church (as a volunteer).  We have two buildings that are separated by 50-75 feet, but there is a wired ethernet connection buried underground between the two buildings which allows us to run it as a single network from a DHCP perspective..  We have a combination of legacy WiFi gear in the two buildings and some donated legacy Wifi equipment that I am trying to figure out how best to deploy to get the best performance and minimize interference between networks (I am not aware of having any significant interference issues, but we could be having some) given we have multiple routers in play (multiple volunteers over many years and no real consistent management of the IT over the years  - I am trying to change that).

Current setup: 

Building A: about 6200 sq ft - Contains our main offices, a fellowship hall, and an old sanctuary.  We no longer use the old sanctuary for our worship services, but we do rent it out to other organizations/congregations.

    - Legacy NetGear N600

          - This router is what is connected directly to our outside internet feed

          - It is not currently physically positioned very well for coverage

                    - Coverage is OK in office area

                    - It has fair coverage in our Building A Fellowship hall

                    - It has poor/no coverage in the Building A Sanctuary used by our renters

          - This router provides DHCP for the entire Campus

          - This router has four WiFi Networks

                    - Building A Main Network (5G and non 5G) - What our offices are on 

                    - Building A Guest (5G and non 5G) - Allows for guest access in our office

    - Legacy NetGear R6220

          - This replaced an older WiFi router that one of the renters had put in place and failed

          - This router is connected into our campus ethernet network

          - This router is providing coverage to the BldgA Sanctuary for our renters

          - DHCP is turned off so that the Legacy Netgear N600 above provides the DHCP

          - This router has two WiFi Networks

                    - SanctuaryA (5G and non 5G) - used by our renters

Building B - about 12,000 sq ft - has our main kitchen, our main Sanctuary, one auxiliary office, classrooms, and a commercial kitchen that is used for various functions including a food pantry.  We also occasionally rent out this space.

   - Currently have an ORBI RBR40 router with 2 RBR20 Satellites that use wired backhaul to the router.in BldgB

           - DHCP is turned off and is provided by the NetGear N600 in Bldg A (described above)

           - Reasonably good coverage across Building B (a few weak spots at the edges, but acceptable coverage

           - Two WiFi Networks

                   - Orbi BldgB - Regular for our internal computers

                    - Orbi BldgB Guest - Regular for guests

           - Orbi networks can be seen in Building A, but pretty week signal

Additional equipment available to deploy

    - Additional unused RBS20 Satellite that could be deployed

    - Recently donated RBR50 and RBS50 (someone replaced at their home, appear to be working but not fully tested)

I am considering a couple of options -

        - Use the extra RBS20 to better cover the weak areas in Building B

        - Use the extra RBS20 in BldgA office area using wired backhaul using the wired connection between building

                - Would still need to use the Netgear R6220 to cover the Building A Sanctuary

        - Replace/retire the existing  Building A Wifi networks with the donated RBR50 and RBS50

I would appreciate any advice and/or feedback you might have.

Jim