We have found that some of the included shore excursion to be quite good, but we avoid the panorama bus tours. If you chose this option, you are effectively paying $100 per tour in the cost of Olife, but you can choose tours up to around $200, so that can be an advantage (Tours above $200, and those with special lettering like OE, OS, etc, are not among the included ones.)
The beverage package is only wine and beer with dinner. All non-alcoholic beverages are included in the cruise fare, without the need for any package.
The OBC can be used for any onboard charges that post to your account, but recognize that you are paying $200x2 for the OLife option, so there are no savings. In essence you give Oceania $400 in advance for you to spend on board, but it is non-refundable if you don't: use it or lose it. Some folks like the convenience, but it is a financial wash.
If you don't like Oceania's included tours, the cruise only option (No-OLife) may be you best bet.
You may know that included air is not part of OLife, and you can have cruise only (no OLife or air), OLife without air, or air without OLife.