What is cold process soap?
A traditional method that keeps the naturally produced glycerin in the bar rather than extracting it, which is why handmade soap feels less harsh.
Which bar suits sensitive skin?
An unscented one first, since fragrance is the usual cause of a reaction rather than the soap itself.
How do I stop a bar going mushy?
Keep it on something that drains and out of the shower spray. It is the single thing that determines how long a bar lasts.
Is a bar better for the environment than a bottle?
On packaging, clearly yes. Whether it suits your bathroom is a separate question.