We study the spectral dimension and asymptotics of Kreȋn-Feller operators for weak Gibbs measures on self-conformal fractals with and without overlaps. We show that the L q -spectrum for every weak Gibbs measure with respect to a C 1 -IFS exists as a limit on the unit interval. Building on recent results of the authors, we can deduce that the spectral dimension with respect to weak Gibbs measures exists and equals the fixed point of the L q -spectrum. For IFS satisfying the open set condition it turns out that the spectral dimension equals the unique zero of the associated pressure function. Moreover, for Gibbs measure with respect to a C 1+γ -IFS under OSC, we are able to determine the asymptotics of the eigenvalue counting function.