I would think that would be best, unless you are running the Vali2's in low gain (presumably gain of each channel is dominated by high precision resistors on the circuit board and not the gm of the tube sections).
@Jason Stoddard might be able to shed more light on this (non-typical application) ...
(added)
in the case of Bifrost 2, both the SE RCA and Balanced XLR stages use the same output circuits, so no need to employ 2x Vali2-- just use a single Vali2 via RCA pre-out into the Jot2 RCA inputs, which will convert the SE signal from Vali2 into balanced differential (Nexus circuit topology).