POSIX SMB mounts are currently case-sensitive only. Just like many POSIX filesystems allow case-insensitive mounts, SMB mounts with POSIX extensions should ideally also allow case-insensitive mounts.
This (case insensitivity) was explicitly discussed and ruled out-of-scope for SMB3 POSIX extensions - at least the first version. I think this should be shelved as a "feature request" until after we have much more experience with working SMB3 POSIX.