If you choose to play through it, there's actually a way to get your class companions back early. I believe it's after or during chapter 9 of KotFE that you get access to a special terminal for that. If you use it to get a companion early, you can still do the recruitment missions for them later, just not with them as your active companion. I would suggest at least playing through the "Knights..." storylines once and then decide whether it's worth it for your other characters.

Floor Safe and Wall Safe are both decorations that let you access your personal cargo hold. They are sold at the security key vendor on the fleet, but you could probably find them on the GTN as well. I'd definitely recommend adding a security key on your account if you haven't already since it grants you 100 cartel coins every 30 days or so.