Hi Chuckies123,
the sx900 is an excellent keyboard with many more sounds than the s770
It has many of the voices of the Genos, except for those of S.Art2
It also has many more DSP effects than the S770, as well as including effects from guitar amps from the 60s (this is if you want to connect a guitar to the line input of the SX900).
I haven't thoroughly worked on VH2, so I can't give you an exact answer.
I know there are many editing tools, in the VH2
it also includes a vocoder for EDM music
The dobro guitar, it's not in the sx900, but
I can tell you that it has more and better than the S770
As for the S770 Jazz Organ patch,
I think there would be no problem, and it would work perfectly on the SX900
I hope this helps you in your purchase decision of the SX900
By the way, I also have a YouTube channel, although lately I haven't uploaded videos, here is one if you want to watch it
https://www.youtube.com/watch?v=vOWU8OlpLfECheers
Hans