21cm brightness temperature power spectra from 21cmFASTv4 runs with differing levels of astrophysical scatter. The top rows show the runs where the scaling relations have a fixed (linear) mean as scatter increases, whereas the bottom rows show runs where the mean is allowed to increase with the scatter (i.e. at a fixed log-log mean relation). The left column shows the epoch during X-ray heating where $⟨d{T}_{b,21}⟩=0$ mK, and the right column shows the midpoint of reionisation $⟨x_{HI}⟩=0.5$. The 21cm power spectra for the mean normalised runs show a much milder evolution with astrophysical scatter, however the scatter still affects the power spectra when boosted 2 to 3 times our fiducial, as might be needed to explain recent JWST UV LF observations.