8 or 9 days is a fairly short amount of time to see two different countries, but since you are focusing on just 2 specific areas I guess its ok. I dont' know anything about Sabah in Malaysia but live in Bali so I do know it quite well.

Bali's unique Hindu religion is a very interesting aspect of travel to Indonesia and Ubud which is about an hour inland is a great place to see it. This week we have a huge temple ceremony going on which is a 1,000 year anniversary and large God figures from villages all over the region are making visits to the temple in long processions. A very wonderful time for seeing Balinese Hinduism in action. However, it has caused a lot of traffic jams so it's a mixed bag for tourism.

If you want a beachy section there are several areas that could suit you, but it depends on your own travel style and likes and dislikes. I personally would spend the whole time in Ubud but that's just me.

And yes, hiring a private driver in Ubud or anywhere in Bali is easy. The biggest complaint usually from people is that there are so many drivers offering tours and they have a hard time choosing as they all seem so nice. You can easily just arrive, walk outside your hotel and pick out a nice driver, look at his car, talk about what you want to see, negotiate the price, and away you go. It can be as simple as a point to point drop off, a per hour rate, or half or full day tours. Easy and very flexible. I personally would not book a driver beforehand because some of the drivers who are "advertised" on the internet become so well known they essentially become booking agents and send someone else to do your trip..How would you ever know if the Wayan who picks you up is the Wayan who actually comes to get you? (Wayan means first born, whether male or female) But all is easy in Bali...really.