unfortunately armor that is soulbound can only be worn by the character that it was originally soulbound to.
However certain gear (weapons most notably) can have the “Account Bound” quality. That quality would allow you to equip it to one character, then unequip it, put it in your bank, pick it up on another character and equip it to that other character.
The easiest way to get Account Bound Gear is by applying the Achievement Chest Weapon Skins to any given Weapon. That will give the weapon a Crystalline appearance, and the Account Bound Trait.
Also, your thread title was a bit misleading. I thought you were asking if you could use transmutation crystals on gear that has gem store skins applied to it. That answer is of course a yes.
Yes, you can. Get a white armor of the same type and transmute it. This makes it account bound. Give it your char, and then transmute it again an armor with the stats you want.
You can transfer it over to your Charr. Just use a transmutation stone (or crystal if the armor is level 80) to transmute the appearance onto a white piece of armor, which should make it account bound instead. Then you can use another transmutation stone to transmute it to your Charr’s armor.
