I've wanted to start my Skyrim character enchanting for a very long time but I'm currently level 50 and with several playthroughs previously with the same problem; that I can't seem to bring myself to soul trap anything if it turns out I'm dooming a feeling creature for a disproportional amount of suffering via the trapping and use in enchanting. I've looked in just about every canon piece of work on souls to find a solution. I managed to come up with this hopefully plausable headcanon that I hope people here can either confirm to be conforming to lore or provide evidence against.

For both black and white, the soul is both the animating force and the the personality/experiences of the creature. However, on death, the personality of a white soul is lost and the soul force escapes unless otherwise soul trapped. So with white soul enchanting it is only the animating force that powers the magicks, which explains the Soul Siphon perk. This explains the ease of white soul trapping compared to black souls. It's Arkay's protection that makes a soul black, and is what allows the retention of personality in order to go onto whatever afterlife awaits (possibly with the animating force separating and going to the Dreamsleeve if no soul trapping was involved). Ghosts are black souls with unfinished business on Mundus who weren't soul trapped. It may be possible for white soul creatures to create ghosts, but do not move on to Aetherial afterlives.

However, through either necromantic ways of soul trapping, or just the greed and lust for power of the dark forces, even white souls retain their personality when trapped in a black soul gem. It may be that the weaker souls are more powerful that way or just for cruelty's sake that this happens. Perhaps for necromancers always taking the whole thing is easier. It may take a while for the personality

This part is more speculative but the being with souls given Arkay's protection are those the Aedra believe are capable of moral reasoning, which is why Falmer lost their protection in their decent into savagery. (Not sure what the policy here for spoilers but just in case, Dawnguard spoilers.)

That's the headcanon. Basically, the soul trapping white souls means only the soul's animating force is used, black soul gems use the whole kit and kaboodle.