In this paper, we first establish a general lower bound for the multivariate wavelet leaders Rényi dimension valid for any pair (f 1 , f 2) of functions on ℝ m where f 1 belongs to the Besov space B t 1 s 1 , ∞ (ℝ m) with s 1 > m t 1 and f 2 belongs to B t 2 s 2 , ∞ (ℝ m) ∩ C γ (ℝ m) with 0 < γ < s 2 < m t 2 . We then prove the optimality of this result for quasi all pairs (f 1 , f 2) in the Baire generic sense. Finally, we compute both iso-mixed and upper-multivariate Hölder spectra for all pairs (f 1 , f 2) in the same G δ -set. This allows to prove (respectively, study) the Baire generic validity of the upper-multivariate (respectively, iso-multivariate) multifractal formalism based on wavelet leaders for such pairs.