I have a Xiaomi mi box 3S (same hardware) and have no problem with 1080p on my hdd but have problems on multiple 2160p heavy movies.
P.S. I have this a WD Elements Portable 1TB HDD (WDBUZG0010BBK-WESN)
Mine plays 1080p MKV with no problems, haven't tried 4k though.
Be VERY careful.
Oreo across a whole swag of Android TV platforms has had exFat and NTFS hard drive connectivity problems, I believe the Mi Box is still affected.
This means you are restricted to FAT32 formatted Hard Drives only. And FAT32 has a 4GB file size limit.
It's only a good choice if you can't afford anything else. If you don't need an ATV don't get the Mibox.
Yes!