Thanks Jedifish, Justinjoyfish, nice meeting all, pleasure to be able to share and meet new friends
For Variable ND, it's normally not advisable for stills as the useable range is about ND32-64 (5-6 stops) even though it states ND400 (9 stops). At the stronger intensities, there's cross banding, have seen on even most expensive brands. Being made of 2xCPLs, it would be expected to have more IQ drop than using a single fix stop ND. Can do a quick google to know about cross banding effect. I would think it's more useful for videos though. If there's any brands that you intend to get, it's best to check online reviews before investing in one.