[MaxiHP]

I have begun the exploriation of OSPF and utilizing it in my landscape. I am very green in this topic I would imagine others have done this however I cant make heads or tails. I have this working using a different method however the admin is tricky I would like to change to a more automated control. Attached is a rough picture of the setup.

First the ATT Fiber comes in and can go to a R7000 "Gateway" (noted red in pic) then Vlan assignments sent to the 2 "easy smart" switches TP-SG108E then out to 3 R7000 OSPF routers each on its own Vlan.

Does the Gateway go in front of the switches or can the switches be between the 3 Vlan routers? eliminating the first set as 10.0.19.0/24

Dose the Gateway R7000 if used is it also to be a OSPF router?
Where to put the High Availability Pihole (2 raspberry Pi 4 8g) currently set as 10.0.20.20 with 249 & 250 being the actual IP.

I have 7 R7000 appliances that can be configured in many different layouts I want to segregate/balance the load between the "gateway" and the routing using Vlan. Again I am green and this could only be a wild goose chase. I have found the installation steps but they are more for users with a better understanding of networking clearly. the searches I have found do not use any Netgear appliances directly I don't know if that is a difference.

It is my hope that someone other than the advances experts can answer this scenario.

Thanks in advance for your help.