I think the OP is asking about the read/write speed of the SSD and not the capacity. But yes, that is about as fast as the interface on these old Macs can handle. I have a 2012 i7 2.6ghz quad Mini with an original Apple internal 256gb SSD. This is how it clocks.
The best it can do is SATA3, which tops out at around 600 MB/s theoretically. There's a little bit to gain on random read/write speeds, if you buy more expensive ones, but don't expect much in real life results.
The 2011 Mini doesn't have USB3 IIRC, but the 2012 does. I booted that same Mini with Catalina on an external USB3 Samsung T3 SSD and used it pretty heavily with Final Cut Pro and Logic Pro for awhile. I didn't notice much, if any, difference, although it did take about 30 seconds longer to boot. On a 2012 Mini, the external SSD made more sense to me. I didn't want to take it apart and an external SSD is a good thing to have for other things in the future.