@Radiant - Since you haven't bought any hardware yet and are just planning, you've passed the first test of this forum, as proctored by the gurus here "Study before buying".
Again, my caveat is that I'm just a newbie, but I would consider an alternative setup to using an NVR, which is running
Blue IRIS (BI) on a dedicated computer. That's what I plan to do. I haven't bought any hardware yet either as I'm still studying. There are certainly plenty of forumites using NVR's but also a strong following in the BI camp.
I'd also consider going with a dual NIC setup on that dedicated computer and setting up a subnetwork for your cameras so they are isolated from your main network. Not everyone goes this route but there's a strong following on this forum to using this network topology. It makes sense to me and I plan to setup my network that way. A lot of the other security measures like OpenVPN are still a little abstract for me but I'm coming around to how that all works.
Can you add a second Ethernet run to your garage area so you can isolate that second POE switch and cameras? If so, consider the sketch below as an option.
Hopefully the gurus can share their wisdom and experience to better guide you.