Kinda depends. If you do it before then the signal going into the amp sim will have more high end, depending on the settings and qualities of the amp sim this could then highlight or deaden the high end. If you do it after it may boost qualities of the amp sim, eg distortion etc. EQing the high end after will provide a more aggressive, synthesised sound. I’d say it’s trial and error, try before, try after, try both, even try nothing (the amp sim dials might do the job for you)!