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It does look like at the moment only 128GB of memory is available for the 5G versions, but do remember that there is a micro-SD card slot that can take up to 1TB of extra storage (I read one report that said 2TB). The WiFi 128GB version has 6GB of RAM against the 8GB for the 256GB version. I haven't been able to find what the RAM is on the 128GB 5G versions, it could very well be 8GB of RAM. I do think the extra 2GB of RAM will make a [minor] difference.
The Verizon 5G version only has 128GB of storage, 6GB of RAM, and only is available in Black (confirmed on their website).