Architecturally similar to my installation.
I have a "core" switch which connects to the firewall, but with one switch port with half the VLANs going from the core switch to the firewall and another switch port with the balance of the VLANs going to another firewall port.
Then, the core switch connects to my two remote switches (analogous to your switch by the firewall and your garage switch).
Without bridging the firewall ports, I don't think you can home-run both switches to the firewall and route all VLANs to both. And Netgate here has repeatedly discouraged using bridging on the firewall.
Thus, a "core" switch is necessary, or, daisy-chain your switches.
A couple of down-sides to daisy chaining switches is the single-point of failure in the daisy chain. If your top switch fiber goes bad, or the top switch goes bad, your entire LAN goes down.
Also, all your traffic then has a single collision domain between your top switch and your firewall. Probably not a real issue on a 10G fiber, but if you have tons of traffic on that fiber it could degrade performance.
A core switch could alleviate the collision domain issue, and if you connect the core switch to your firewall with two fibers, one for half your VLANs and the other for the rest of your VLANs, you'd remove a single point of failure for your entire LAN at least as far as the fibers go.
If the core switch fails then everything fails*, but that would be easy to diagnose. If just one fiber or fiber port goes down, only half your LAN (one of your two switches) would go down and that would be easy to diagnose.
YMMV.
*You could certainly design some kind of redundant core-switch arrangement with spanning-tree protocol and multiple switches and fibers and so on, but that's out of my league.