Alternative. You can unofficially upgrade the Synology with 2.5GbE via USB. But in the end, this is only useful if the NAS or the hard disks can provide this.

https://macandegg.de/2021...
https://github.com/bb-qq...

No, because although it is mathematically 2Gbit/s, the second connection is actually to be seen as pure redundancy. In total, the bandwidth remains at 1Gbit/s.
The exception would be if your switch supports link aggregation, then you can expect more bandwidth.