Open-E uses XFS file system on the storage with 8k blocksize, so if your storage will be big enough then it will work.

8k block size * 100 millions Inodes = 800GB for volume

Of course it is when files are not greater than 8k.

BUT I do not suggest you to have those files in one folder - listing them will take almost forever

Did you think about using iSCSI instead of NAS? I suspect that SMB and NFS protocols could not handle such count of files. iSCSI protocol is block-based and will work much better.