As an offroad newbie, I'dd say a 990 is a big challenge.
I own a BMW650 Xchallenge, same category as the 690 and I do everything with it, allroad, offroad even enduro like, but also long roadrides.The engine is strong enough to give you plenty of fun on the small twisty roads and the lack of weight makes it even more a fun bike. I have even done 900 km on the motorway in 1 day, no problem, but not as comfortable as on a 990 offcourse.
Only 2 up is a bit limited I think, the engine is strong enough until you go on the motorway, 120km/h can be challenging, but also the bike is quite small for 2up. Small rides should not be a problem I think, only I believe there are no pillion pegs on the 690, but I have seen them aftermarket. And also make sure to invest in a proper seat, for yourself and the pillion