I saw only one comment answering OP, I’ll add mine.
I use an n150 motherboard with 16Gb of ram.
It is the same CPU with a better GPU (in short).
I have 3 SSD attached (plus boot SSD), and 5 SATA drives as well, and an integrated 10Gb Ethernet connection.
It manages to download at 6-8Gb/s, and in general, it largely delivers the maximum capacity of WiFi, and 2.5Gb/s Ethernet as well for the hard drives.
It also has some containers, and half of ram is used for services hosted by Truenas, and it works well.
So, here, OP just wants to use his NAS as a NAS without services attached.
The n100 with 8Gb is going to be weeeeeeell enough for him.
The RAM upgrade might be a plus though, so look if you can replace it later.
In short, the n100 on a 2.5Gb connection with 8GB of ram is well good for you, as long as you use it for SMB only.
For more stuff, add more ram. 16GB is the minimum. 32 is the recommended minimum.