Trimmer, no ingrown hairs.
I ride a TT bike with a tri specific saddle. Meaning it keeps the pressure off but still will bunch that area more. So, it's more comfy to take care of business down there.
But, no shave.........just do a nice purpose built trimmer for the job. They sell personal trimmers. Some even come with a wand if there's some back hair to deal with.
Not a fun topic, but a good one to get right in the spirit of preserving a good and healthy body.