Just FYI - I currently have a J4125 based device with 4 x i225 NICs & 16GB RAM and it runs Proxmox with OPNSense, docker and PiHole without issue . . . I pass two of the physical NICs from Proxmox to OPNsense via immu (PCI passthrough) - So the N5105 is enough for such tasks - YMMV
Still, I broke down and got myself a Ryzen 5800U unit - only because I think for the price performance - this is one hell of a Proxmox/Firewall combi device
The J6413 is a tiny bit more power efficient - but the savings are not substantial to counter the uplift in price . . . Have fun!