Well I guess I can give you first hand experience of the latter part of your question.
I do a lot of fishing, I usually go on days that end with a 'y'!
I had a naked GS500 that I used for everything (piccie attached) - the engine was punchy enough for motorways and it loved rough terrain - to compare it to the Inazuma in my opinion is like comparing twins, only difference is one was faster! Due to divorce I reluctantly had to sell it.
After divorce / money was finalised I too had a scooter - I fitted a tow bar and towed a trailer of fishing gear over all terrain. Due to the light weight of the bike it performed well but the wheels were too small for muddy or rough terrain - thankfully it was stolen.
When I had my Inazuma I fitted a tow bar and towed a trailer laden with fishing gear over 'back roads' across fields and along canal towpaths. Although I rarely rode quickly across these area's I never 'held back' and the little Inazuma never let me down. Bumpy roads were handled with ease and due to the light weight of the bike it never got 'bogged down' in mud.
I am not 'fat' but am 'XL' size and I always keep my bikes rear suspension set at the 'mid point'.
I really loved my Inazuma and it could do all that I wanted i.e. 70mph down the motorway or transport me to the fishing venues laden with gear.
But then the darkside got me! I brought a Harley Iron 883 which although could cope better than the Inazuma on motorways (obviously) it simply was all over the place on bumpy terrain - show it a patch of mud and it would show you how quickly it could get stuck! It was too heavy and vibrated everywhere. Bad road surfaces were noticeable! I did not fit a tow bar as the bike was simply too much of a challenge on rough terrain. Unfortunately (perhaps fortunately) it got stolen.
I then brought a Harley 750. This bike, and I have had more bikes than I can remember, is the best I have ever had. No vibration and a cruise that is so comfortable your granny would fall asleed as a pillion!
BUT, again when on muddy ground the bike is simply too 'big' and heavy (although lighter than the 883) to not get 'bogged down' and the rear tyre is so thick that mud gets everywhere.
I now have an electric pushbike and trailer for fishing.
So to answer your question, although I have had trail and trials bikes that would 'p' all over the Inazuma on rough / muddy roads out of the 3 x bikes mentioned above the Inazuma performs best over 'all' terrain.
Will I buy another? If I had the need for one in a heartbeat I would, But I now go fishing on the electric cycle and enjoy cruising along at high speed in comfort too much to look back!