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I never tested R+A or B+D. It seems concentration of targets is good for
piece value, though. On Knight vs Commoner this effect is overshadowed by
the slowness of the Commoner. But I would expect R+K (R+F really) to be
better than R+A, as the speed there is set by the Rook component. But only
slightly better.

For B+D I am pretty sure it must be worse than B+K (B+W). Not only because
of the smaller target concentration, but also because B+D is color bound.
Now color bounding is not a big deal if you have the pair. But it will mean
there is a large pair bonus, probably larger than the 50 centiPawn pair
bonus for orthodox Bishops. So I expect a pair of B+D to be marginally
weaker than a pair of B+K. But in the former case, 70-100 cP will come from
the pair bonus. And in Spartan Chess you have only one, meaning that it
will be some 50-65cP weaker then a single B+W.

I once tested B+K and R+K by crowning the Rooks of one side, and the
Bishops of the other, in an therwise standard FIDE array. IIRC the Crowned
Rooks had a slight edge there, but less than half a pawn in total. Standard
orthodox values (from Larry Kaufman) are B = 325, B-pair = 700 and R = 500.
The B+K pair tested 50 cP stronger than two Rooks, so 1050, a 350 cP
increase by crowning. Two B+K gained a bit more, so ~1380, so 690 a piece.
On that scale R+N = 900 and B+N = 875.