My doctor has said that if the strings bothered my partner during intercourse he could cut them off when I revisited. He never trimmed them, they are the same length they were as when the doctor took the IUD out of its box.
The strings arent really long enough to get attached to a toy and keep it inside you if thats what you are worried about. You will never have that issue.
My partner rarely feels them. In the three years i've had my IUD he's had to make me stop piviting when I was ontop maybe two times bcs it was too intense for him, the rubbing of his tip on the strings.
Don't worry about the strings! They will not interfere with your toys.