Focusing on those specific examples, you usually have a combination of different consultancies and vendors - not a single stop shop.
Companies like this will usually have an internal team who oversees things like interior design guidelines, probably working with outside vendors to create the retail experience. That probably consists of lots of pages of raw plywood design guidelines, stainless steel art pieces, furniture types etc.
Each individual franchisee will then usually get that branding guidelines and have to pay an architecture firm to actually apply the guidelines to the actual design of a specific building, and those plans and designs will all need to be approved “through corporate”. You see the same thing at retail stores, car dealerships, etc. Usually when one “new design” takes over, every retail presence has a certain period of time in which to comply.
For things like the IT experience, you will usually have a VAR (Value Added Reseller) who’s job it is to assemble things like the entire set of payment kiosks, kitchen display monitors, etc. They aren’t a design consultancy in this case, but someone who packages up a bunch of existing hardware from enterprise companies to stitch together a solution for the retailer and sometimes layer some branded software on top of it.
Website/app stuff would all be owned by the corporate entity and tied into those back end systems. This is usually outsourced but I have seen some companies that have internal teams for this, and many companies leverage existing platforms (like OLO) to deploy this rather than building or designing anything from scratch. That type of work can go to any typical digital agency.
The challenge with being a one stop shop consultant is companies usually don’t like their contractors managing sub-contractors (especially on massive multi-million dollar projects). So even if you were to get in the door for providing one service, they would rather manage the contracts for services that you can’t provide end to end themselves.
Again - not to say it doesn’t happen, but most consultancies that exist in this space are multi-region power houses that can leverage skills of different studios as needed for big projects. My daily go-to consultancy has a UX team in NY, a traditional digital agency in UK, and developers in Eastern Europe rather than everyone under one roof.