For accessories that are 30” wide, you’ll need the 36” cabinets, and for accessories that are 19” wide, you’ll need the 24” cabinets.
When combined, I had one 5-foot base and one 7-foot base that flank both sides of my standalone Aspire by Hestan gas grill.
Be sure to plan out space for your cabinets and grill, plus space to walk around and hang out and room for patio cover columns, if you choose to cover your outdoor kitchen, which I do recommend.
Once your cabinets are built and connected and you’ve figured out what material you’re going to finish the sides with, you’ll know how wide the base cabinets will be.