Convert from extending L2 (VLANS) to L3 routing

I have included a diagram that I quickly put together, https://i.imgur.com/275InwS.jpg

This is the current scenario, I'm extending L2 networks (which reside on the sonicwall) to each building (via fiber) into 48 port edgemax switches. There are about 7 buildings total, they are configured the same as building 1,2,3 in the drawing. All buildings share the same VLANs. Each VLAN does something specific (I have more than 4, but for saving space I only used 4).

For example:

• VLAN 1- LAN
• VLAN 2- WLAN
• VLAN 3- Guest WLAN
• VLAN 4- IP Cam Network
• VLAN 5- VOIP Network
• VLAN 6- Printer Network

My IP Camera Network is 192.168.4.0 /24 which means any IP Camera related component located in any building is assigned a 192.168.4.0 address from the DHCP Serve (Sonicwall). Same concept for LAN, WLAN, IP Phones, etc....

There is some redundancy in the network, I actually have two sonicwalls, configured in HA and two edgemax 16 port fiber switches in the main office, but I only included one of each in my drawing. Instead of two fiber cables going from each building to the edgemax 16 port (in my drawing), one fiber cable goes to one edgemax 16 port fiber switch and the second fiber cable goes to the second edgemax 16 port fiber switch.

Each building, however, only has a single network switch. That works for me (in this scenario) since the devices connecting to the switch only have one NIC.

Regardless, this question is more about routing.

I'm not looking to make any changes at this time, I'm trying to figure out the best way to set this up in a new environment (new property, new site, etc...) or if a rebuild were to happen, down the road, what could I do different.

Here is where I struggle....the design. I'm not sure what the best way to design this would be.

Do I start by going to the sonicwall, building a pt to pt network (/30) from the sonicwall to the first 16 port edgemax switch? Then building a second /30 from the sonicwall to the second 16 port edgemax switch?

From there, I'm not sure how each building talks back to their respective edgemax switches. I'm picturing everything having it own network and the routing protocol takes care of best path (if a link were to go down, etc).

At this point, this is more for learning, I'm not looking for configuration for each component. We do use a VAR and I'm not the only one on the networking team, but the others on my networking team don't want to discuss these types of things. They are either glorified help desk techs or 'older' and are set with how things are and even though I/we are not looking to change things, they don't want to waste time talking about it. With that mindset, I can't get anywhere with my internal resources. I'm sure the VAR would help even though it isn't cisco gear, but they'd also bill for their time, which is understandable, but not something I could approve.

Thanks in advance.

edit- changed /32 to /30, a mistake on my end.