In my experience, the local management GUI is currently taking a lot of CPU from the box; it is suggested to open Embedded GAiA WebGUI only when needed, not for constant monitoring. The SMB appliances are very easily configured when used in Stand-Alone deployment for simple environments. Preferably, only a few rules have to be created and a lot is just configured by defining the corresponding objects. If you want to use a complicated rule base, i would suggest a centrally managed SMB unit and R80.10 SMS. This will give you much more possibilities (services excluded from VPN, user.def, crypt.def, vpn_route.def and many more) without taking performance from the GW.
CCSE CCTE CCSM SMB Specialist