I used a pocket bow press to relax the pressure on the string when I replaced mine. My only concern was damage to string fibers if I forced the old peep out and new peep in with full pressure on the string.
I've not tried a string splitter. the possibility that it might fray the string would be my concern. hopefully other folks could speak from experience on this.
If it was me, I'd use a press. I have one now, but before the string splitters worried me too much...lol.