Generally speaking most of these warnings can be safely ignored.
In particular, the warning about the app_addr length will not negatively affect this sample, as the highest address bit will simply be ignored by the MIG core (because the MIG core address range is shorter than the other modules). Reducing the app_addr length in the other modules may reduce some utilization inside the device, but it is unlikely that it will impact anything significantly. If things were reversed and the MIG had a wider address range there would be an issue (as we would be unable to address the full memory), but that is not the case here.
Many of our endpoints generate a lot of unconnected signal warnings on okHE/okEH due to the fact that not all endpoints use every signal on those busses. These warnings are safe to ignore and difficult to remove.
Warnings from inside the okCore module can be safely ignored.
Generally speaking, FPGA design differs from software in that warnings cannot always be avoided. Oftentimes the shorthand used to make an FPGA design more readable/workable result in warnings as well (like those related to the okHE and okEH signals).