I boot my RPi 4 entirely from USB with the Sep-3-2020 bootloader. No sd-card inserted. The Sandisk Extreme Pro benchmarks at 230 MB/s on USB 3.0.
The Samsung T5 and T7 are frighteningly fast USB-attached portable SSDs - some simple tests of mine had them at around 335MB/s. On paper the T7 should be twice as fast, so it's interesting that they tested so close (the T5 was even a little faster, as high as 350MB/s), but they are both totally good enough.