Using USB3 / USBC external storage for years.
Buy a good, non cheap, USB jbod or raid enclosure and put SSDs in it!
I have a 4 bay USB3 jbod plus a 2 bay USB-C box, inside the disks are all RAID.
Indeed internal disks / ssds / nvme are better, but consider that speed wise even USB3 is faster than any WiFi.
Just don't but they cheap and use good cables. And if you use spinning disks, ensure they stay cool.