Yes, the Fujifilm X100VI is compatible with the Lexar Professional 1667x 64GB SD.
Lexar Professional 1667x 64GB SD is V60 class. Meets the floor for: 4K30 (30 MB/s floor). (Peak write 120 MB/s is not evidence of sustained performance; the V60 class rating above decides this.)
“Fujifilm X100VI specifications: storage media is SD/SDHC/SDXC with UHS-I — UHS-II cards operate in backward-compatible UHS-I mode and meet all recording requirements.”
Last verified:
Compatibility inferred from spec rule (citations above are manufacturer-verified)