As you know, deeper seating in handgun rounds produces more pressures & often higher vel. As to accuracy, I doubt any shooter can tell the diff. So there is no rule of thumb, as diff powder/bullet combos will react diff, but the only rule I know is seating deeper WILL increase pressures.
Now rifles are a bit diff. It's a good rule of thumb to keep at least one caliber length into the case mouth for rounds that have to feed form a mag. Less than that & the bullet can be "cocked" as it hits the feed ramp. You lose neck tension & accuracy, so for rpeating rifles, bolt or semiauto, I stick to the one caliber minimum. On my single shots, you can go as skinny as you like, but the one caliber rule works for me.
"Given adequate penetration, a larger diameter bullet will have an edge in wounding effectiveness. It will damage a blood vessel the smaller projectile barely misses. The larger permanent cavity may lead to faster blood loss. Although such an edge clearly exists, its significance cannot be quantified".