As far as I can understand, reset controller is completely independent block, it does not bring up platform PLL before loading RCW data.
Reference manual says:
Initially, the RCW source POR configuration inputs are sampled to determine the
configuration source. Next, the device begins loading the RCW data. The system PLL
begins to lock according to the clock ratio/mode values communicated in the RCW data.
For second question - I do not see any errata related to booting from 32-bit eLBC GPCM NOR flash, nor to PBI loading.