I've played around with the traction control on gravel, my findings:
Level 3 is like an over-protective nanny, it will stop pretty much all wheel-spin on gravel and make it feel like your bike has the power of a 100cc bike.
Level 2 is much better, some wheel-spin, feels like you have a more powerful bike, but with control over excessive wheel-spin.
Level 1 is much looser, you can feel the rear wheel going sideways as is spins - you definitely want to be careful with the application of throttle with only level 1 TC.

G mode is for gravel or dirt, it changes how the clutch engages. Supposedly putting it into G mode is the best for dirt/gravel/loose surfaces and turning it off is best for a sealed road.

I haven't seen any mention anywhere of the AT having linked brakes, I suspect that on an adventure bike you want a little more control and therefore want the front and rear brakes to be completely independent. If I'm wrong then would someone more knowledgeable please correct me.

DCT Modes:
D - Don't use*.
S1 - a good all-round mode, works well.
S2 - good for sportier riding, will hold in lower gears longer.
S3 - for when you want to ride more aggressively, will let you hold lower gears way longer. Good for maximum acceleration and maximum engine braking.
On M, D, S1, S2 & S3 the up/down gear selectors on the left side work - you can get the bike to change up or down gears even when not in M mode.

* Note: you can use D mode if you want, but I wouldn't. I found it changed up gears too early and would put the bike in such a high gear that it was useless. By 60kph it had the bike in 6th gear, I was much happier in 5th at that speed like S1 went with.

 

DCT Modes:
D - Don't use*.

Or as my wife says D = Dead Boring

 

When I first got my AT, I was constantly using S3, now I use D more on local and freeway
and S3 when I want to be more aggressive
S3 holds 1st too long for comfort when turning from a stop

 

Have you thought of trying S1 instead of D? There is also the option of telling it to change up when you think it is holding a gear too long, there's a button on the left side for that!

 

My own experience - on roads only re DCT -

D is next to useless for me unless I am on my gravel drive, or in heavy stop start traffic - otherwise mine lives in S2. For me this is an OK compromise - so I am in S2 95% of the time. The DCT 'learns ' this so on a one click it will change between those 2 settings. This suits me, then if on the very odd occasion I want S1 I hold in and let it cycle through modes to what I want. I often think to try it in M mode but never seem to get around to it in coming up 5k miles. On roads T has always been in 3 - or nanny mode if you like!
John

 

For long straight stretches of tarmac, I cruise in D. According to Honda it is the most fuel efficient mode. Might as well save gas of the boring sections, but go to S1 or 2 for the funner sections. I haven't played in S3 much yet, but it does seem like fun for more spirited riding, as is manual mode.

 

You are correct on the traction control and the sport modes. The ABS can be turned off to the rear wheel by holding the button for a few seconds. This will allow you to slide the rear tire into a corner, or on a downhill if you want to, while still retaining ABS on the front. G button, or Gravel mode is supposed to be better for the off road stuff, I use it, but I'm not sure just what the differences are. I figure the 6 figure design engineers are probably doing that for a reason. As for the traction control in the dirt, I find that in any kind of rough uphill corners, or in any sand it just cuts off the power. I just turn it off in the dirt, but you have to use throttle control because it can most certainly get away from you in a corner. S-2 seems just right to me for how I like to ride. It will still respond to throttle and brake input and shift accordingly. The paddle shifters will still work, but I find if I want to upshift on a long downhill with the throttle off, once I force an upshift it will no longer hold the gear until I force a downshift again. Say I want to go to 3rd coasting down a hill and paddle shift from 2nd, it will soon go to 4th even 5th, but once it goes to 4th, if I shift back to 3rd it will stay there and I get the gear I want, at least until I throttle up, or slow down. Note, you have to stop to set Gravel mode, or turn off the rear ABS. Hope that helps.

 

I did a very unscientific test with G mode on my ATAS, its new to me so still getting used to the DCT. Anyways the entrance to my garage is up a steep short muddy (in wet) incline and I found getting the bike up seemed to take more revs than I was expecting in D (non-G) being used to riding manual clutch bikes up the same rise. So put it in G as my dealer at handover told me it gave a more direct drive via the clutches. And I have to say it did feel like the clutch(s) wasn't slipping as much as it did in normal mode though still not as direct as a manual gearbox/clutch. ...

 

Jarrett - Obviously, you will get a lot of different opinions, but for what it is worth, here's one more. In summary, I agree 99% with what KiwiMark wrote.

For me, I ride as follows:
On Road - TC to 3, Mode to S1 (change to S2 or S3 if you want to be more aggressive)
Off Road (not in sand) - TC to 1, mode S1, G Mode on (I have found TC set to 1 is a good balance between getting power down with minimal wheels spin, but it is not so aggressive that it inhibits getting up slippery hills OK)
Off Road in sand - TC 1 and manual gear mode so that I don't get any unexpected gear changes