It's a kinda personal thong...did I just say thong?....thing... but for two usb outputs you could put this into this in to one of the inner panels.
https://www.ebay.co.uk/itm/12V-24V-T...EAAOSw4PxaHRMQ
Cheap as chips and works.
As for sat navs...... well there are a few threads on how to take a direct (ignition-on-only) supply from behind the panel that sits under the rev counter. It's a spare Yamaha plug that is linked to the 1st fuse (from memory ) in the fuse block under the seat. People have cut off this original Yamaha connection of the free end snap connector and hard wired their sat nav supply to it. Ignition on equals fused supply to the sat nav.
As for heated grips, that is another choice thing with a lot of riders going for a relay circuit option whereby the ignition-on provides a source of 12v to trip a relay that then in turn feeds the heated grips. This removes the worry of forgetting to turn off the grips when you park up after a ride......as in....ignition off is grips off. Also searchable on here.
The 660 generator has a poor supply for extras and will be quickly used up if you run heated grips / heated jacket / riding spot lights and other toys. The generator uses approx 115 watts just to keep the ECU and the bike running leaving something like another 100 watts to mess with. Take more than that and you'll be riding in power defecit and causing a flat battery and all sorts of other issues.
The above numbers are from memory and may be a bit fudged by red wine at the time of writing....(yes, I know...it's early).
All the info is fully searchable in this forum...Enjoy !