Magnetic excitations in the optimally doped high-Tc superconductor Bi1.5Pb0.55Sr1.6La0.4CuO 6+δ (OP-Bi2201, Tc 34 K) are investigated by Cu L3 edge resonant inelastic x-ray scattering (RIXS), below and above the pseudogap opening temperature. At both temperatures the broad spectral distribution disperses along the (1,0) direction up to ∼350 meV at zone boundary, similarly to other hole-doped cuprates. However, above ∼0.22 reciprocal lattice units, we observe a concurrent intensity decrease for magnetic excitations and quasi-elastic signals with weak temperature dependence. This anomaly seems to indicate a coupling between magnetic, lattice and charge modes in this compound. We also compare the magnetic excitation spectra near the anti-nodal zone boundary in the single layer OP-Bi2201 and in the bi-layer optimally doped Bi1.5Pb0.6Sr1.54CaCu2O 8+δ (OP-Bi2212, Tc 96 K). The strong similarities in the paramagnon dispersion and in their energy at zone boundary indicate that the strength of the super-exchange interaction and the short-range magnetic correlation cannot be directly related to Tc, not even within the same family of cuprates.