As safe as it can be, considering they're a male convicted rapist, then a male prison is the right place for them.
Then guards need to keep an eye on them, but again considering they are convicted criminals and they are male, then yes, the male prison ward is the right place for them.
Same again, considering they are female convicted criminals then a female ward is the right place for them.
Considering "trans women" are males, then yes, they should be in a male ward. If its not safe for them then they should be offered protective solitary custody, or a trans ward if sufficient numbers exist, but they should not be with actual women on a women's-only ward when they are males who have been convicted of rape.
No games.
That you are so far gone that you don't see the problem with putting male convicted rapists in a female only ward, when women have no place to go as they are locked there as prisoners but you're going to add male rapists into the mix shows just how mad you have become.