No, Fingbox should not slow down your network.
This is because Fingbox is only passively monitoring the network: unless you pause/block devices or use ‘Bandwidth Analysis’, Fingbox is not sending any command to any device – it only periodically performs queries about network status (ARP, Bonjour, UPnP, NetBIOS, SNMP, etc).
What to Do if I Think Fingbox is Slowing Down My Network?
You can first try setting your Fingbox to a slower network discovery – this means it will send fewer queries out about your network status.
To enable slower network discovery, click on your icon in the top right-hand corner. Then select Fingbox Settings and enable Slower Network Discovery.