Implants are in variable sizes (from XS - XL). Most surgeons keep S and M sizes on hand and can modify some of them to an extent depending on what they are made of. I would make it clear that you want smaller ones. Everyone I've talked to has been able to choose their ball size.
There are two different kinds of scrotoplasty. One is the VY method which essentially cuts and rotates the labia majora into a hanging sack, and the other "old" method where implants are inserted directly into the majora.
I have the "old" method. I do not think I would have any issues with penetration if I still had a vagina based on where my implants are settled. I could see a VY scrotum hanging too far in front or, depending on how low it is stitched on the back end reducing the size of the opening slightly. But it is the method I'm less familiar with, so I would get a surgeon's opinion on that or talk to someone that had this combination of procedures done, if possible.