My take on this is: RB and VRB are logical definitions while PRB is the effective physical allocation into the time and frequency domain grid.
There is a 1:1 map between RB/VRB and PRB size, and it is important to remember that theorethically, a PRB lasts 0.5ms not 1ms.
3GPP TS 36.211 version 15.8.1 Release 15 6.2.3 Resource blocks
Resource blocks are used to describe the mapping of certain physical channels to resource elements. Physical and virtual resource blocks are defined.
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A physical resource-block pair is defined as the two physical resource blocks in one subframe having the same physical resource-block number nPRB.