[@Nanashi Ninanai]
Greetings, dragon rider.

As far as I can tell you can make small tweaks as you see fit, but nothing that changes the Servant's tale too much, so don't twist them too much. Gender is seen being swapped all the time in Fate, but always turning male historic figures into women and not the other way around.

Out of curiosity, what Servant do you have in mind?

[@NachoBachoPacho]

As far as I know the fame of the hero influences their strength by granting a significant boost when they're at their land of origin (I.E. Cú Chullain would be stronger in Ireland than anywhere else), but heroes with worldwide fame would be stronger than usual, like Heracles. I'd treat it as a bonus over their natural strengths rather than the basis for them, so do increase his physical stats a bit.