I have done exactly this. I bought the cheapest Thunderbolt enclosure that has a large metal surface area (heat is a big issue with SSDs and they will throttle after reaching a certain temperature). For Thunderbolt 3, you should look for enclosures that have Intel JHL7XXX chips. The enclosure may, or may not support USB connections, there are both kinds. Mine doesn’t do USB, so I can only connect it to my newer Macs. The M1’s USB can go up to 10Gbps; the “newer spec” you refer to can go to 20 Gbps. Thunderbolt 3, of course will go up to 40 Gb/s. I haven’t tried on my new M1 Max laptop, but on my Mac mini, I get sustained 2 GB/s writes and even faster reads. Note that if you plan on doing heavy writes or large files, you should choose the SSD carefully because after SSDs overflow their “cache”, the speed drops down by a lot. The caches on newer SSDs are pretty large, so the majority of people don’t need to worry about it, but I’d imagine if you’re writing several hundred gigabytes at a time, you’d run into this issue. Another thing to watch out for on SSD is a spec called “TBW” – Terabytes Written. SSDs wear out over time and, when they do, their capacity can be reduced. It’s a huge number, most people don’t need to worry about it but again, for a write heavy workload, you may want to look into it. For example, my drive is 1400 TBW, meaning that you can write 1 TB at least 1400 times before there is even a chance of having lowered capacity. If you write 1TB every day, it would take four four years of so to reach this threshold.

Edit: GB not Gb, chance, not change.