Bali... Forget about the rivers man, you got waves!
For flooding rivers that you don't know very well. I would say go for a 10'6 C4 ISUP.
If you think you have some nice deep rivers, with clean lines, you can go for an Epoxy board. I would say the 10'6 CMAC ATB. The TEC construction on this board is one of the toughest out there, but you can still ding it pretty easy. There are a lot of river paddlers that really like this board, it has a good combination of stability and performance.
Also it does surf well.. A little extra rocker makes it more forgiving for those late drops..
I have surfed an inflatable and had fun, though it is not ideal.. If i had a chance, and I was in Bali, I would want an epoxy board for the surf, that I might take in the river a couple of times..
PS (I AM THE REP FOR C4, SO TAKE IT AS A BIASED REVIEW)