I have a CG. With the fine bag, I really don't think you will need the disposable bags, but let us know how they work since you've already paid for them!

You can use the PB for the whole pool. But, I think the combination of a PB plus an automatic of some sort makes more sense, especially for a larger pool. I have the PB CG and a Pool Rover Plus for my 20x40 IG vinyl. I went for a month or so with just the PB, but covering the entire pool required several bag cleanings and I had to be there the whole time. My Rover cleans 95% of the pool in 2 hours and I only have to spend about 5 minutes on setup and cleanup.

I normally run the Rover every other day and use the PB to spot clean whenever. Its a great combo!