A person who hides things may be called sneaky. An urban word for people who hides things may be shady.
Someone who hides their emotions is often referred to as "emotionally guarded" or "reserved." They may also be described as having a stoic or poker face.
Someone who hides behind a hypothetical situation can be called an "armchair critic." This term refers to someone who criticizes or provides opinions from a safe and hypothetical position without actually taking any real action or responsibility.
customer
Arch
Chemist
a tanner
Hollandophile or nederlandophile
Crazy.
A person who does things for others may be an assistant or a helper.
adventurous
frivolous
A Philhellene.