Hmm, I don't know that model? It doesn't seem like it is a supported RMerlin router?
I didn't say it is faster afterward. It just works as fast as a USB 3.0 port/drive used.
It is slower to set up than when a USB 3.0 drive is set up in a USB 3.0 port but in actual use, there is no significant, real-world difference between USB 3.0 or USB 2.0.
The only time you will notice it is perhaps when doing a script update, and only in comparison with the same router, the same network, the same scripts and the same load on the router and you happen to be using a USB 3.0 port with a USB 3.0 drive.
On many routers, the USB 3.0 port will cause interference on the 2.4GHz band when it is being used. Use search for more information.
The USB 2.0 port won't be a detrimental aspect of a swap file in the normal use of the scripts. Except maybe for spdMerlin, but if your ISP connection is that fast, you don't really need spdMerlin running either.