I believe. I’ve looked up adapters to be able to change the plug to thunderbolt 3 and they are available,
That's what you'll need if you want to keep using the G-RAID (assuming it doesn't have USB
3 as well).
All you should need is to add the TB3-to-1 adapter to your existing setup. There's no reason not to keep your display daisy-chained
unless it gives you problems, and a 1440p display plus a Thunderbolt
1 hard drive shouldn't be a bandwidth issue. It's exactly what you're already doing with the Mac Mini anyhow.
You need the TB3-to-1 adapter
anyway so suck it and see. If you do get problems then, yes, run a USB-C to DisplayPort adapter straight to your iMac - but if it ain't broke, don't fix it.
Your old USB hub can go into any of the USB-A connectors
or to the second TB3 port via a USB-A-to-C adapter.
There's no speed/performance advantage either way - it just comes down to whether you prefer to use up a USB-A port or a TB3 port.
I’m wondering if when all is said and done, would I be better off just buying a dock, such as the Caldigit and be done with it?
Only if you actually need more ports than the iMac has. Unfortunately, all of these docks are designed for MacBook users, so you're wasting money on extra ethernet ports amd 90W chargers, you're not getting
that many extra USBs
and you'll still need that $50 TB 3-to-1 cable to connect your G-RAID.
The thing to think about is whether you're likely to want to swap your G-RAID for something newer in the near future (again, not broke: don't fix - only super-fast SSDs or
huge RAID arrays need more than 10Gbps TB1)