Under the assumption of waste separation, do boreholes make more sense for specific waste streams? E.g. FPs (fission products) or TRUs (transuranic waste)?

Yes, the borehole specification and canister design allows for a variety of high-level radioactive waste, including a wide range of spent nuclear fuel types. The waste forms would need to be an appropriate size and shape to be packaged into canisters that fit into a borehole.