Ah, well we don't really get a NAS for speed, I'm afraid (despite manufacturer claims that they are 'speedy' and can stream 4K
Even running over 1Gb ethernet, a NAS tops out at about 130Mbs (and with other overheads this is more realistically a max of about 110Mbs). A modern local HDD can do about 200Mbs, and a fast SSD about 500Mbs. So you can see that local storage will outperform your NAS (oh, and that you are not getting the full benefits of the SSDs in the NAS). You'd need to bump up to 10Gb ethernet ...