I have no experience of using hubs, but I wonder if using a hub as a pass-through to a non-USB3 device (eg a T7) doesn't alter the fact that the connection is not ultimately to a USB3 device; so I suspect that your second option may be the way to go. Regarding transfer speeds, even plugging my 2TB T7s into my Studio TB3 ports I can only get write speeds of about 800 MB/s and read speeds of 600 MB/s. And with my 4TB T7 I can only get read speeds of less than 300 MB/s. But I still use my 4TB T7 for my photo files because it's bigger than my internal storage, and I don't see a difference in access times between accessing my 50MB files on the T7 or my much faster internal drive (which has read and write speeds in excess of 5000 MB/s).
In practice I find, comparing my Studio box against my 2015 iMac, I definitely notice the difference in processor speeds, but not read/write speeds; but whether this matters presumably depends on what we are using our machines for.
