I’ve used a QNAP TS-453BT3 for the past 3 years. It has 4x12TB 3.5″ drive as RAID5 so I get 36 TB usable space on it. I can connect two systems directly with thunderbolt and one with 10GigE plus 4 systems over GigE.
Its portable and to carry it around I use one of those bags which are used to keep soft drink and beer cans cold. That’s padded and waterproof. I actually have two of them one inside another for extra protection.
I have one iMacPro connected over 10GigE and two MacBook Pros over Thunderbolt. When multiple systems read or write, the speed drops since its a 4-bay RAID. But any one system on its own, gets me between 300-500 MB/sec depending on the type of data. Frame sequences read and write is slower than large file read/write.
There is also space inside for 2x SATA SSDs and I did try to put two in there, but that didn’t help much as a cache. If you use those two SSDs inside as independent drives, then that might be useful in some way, maybe as a scratch drive or a cache.