NVSRAM has been around for ages, originally from Simtek and ZMD (20 years or more ago).
Basically, each bit is an SRAM/EEPROM combo. When powering up, the EEPROM content is transferred to the SRAM cells, when powering down the opposite happens. This all happens in one go as parallel bit-to-bit copy.
It's a perfect replacement for the (now mostly obsolete) NVRAMs, you know, the SRAMs with a piggy-back battery.
Only downside is, the device needs an external capacitor to provide programming energy when powering down (might be that never devices have the cap internally).
Cypress is the main supplier today, but the Microchip parts seem to be the same.
FRAM is newer, and is a non-volatile drop-in replacement for SRAM. Suppliers are Cypress and Fujitsu. There is no "mirror SRAM" or something like that, the bits are like normal SRAM cells, but with FRAM storage capacitors that keep their state after power-down.
These are true NVRAM/SRAM drop-in replacements.
Both NVSRAM and FRAM have access times like normal 32K x 8 or whichever size SRAMs.