you should never need to move the socket. the origin for a gun would be where the grip is and the origin for the spear would be where the hand holds it.
and yes you would play animations for the character mesh and the gun at the same time. for example fire gun input pressed → play gun firing animation on the gun → play recoil animation on the character.
over all its pretty simple. most items will sit in the players hand in one of two ways, either up or down. so when you import a melee weapon you would have it in the same orientation as the ib weps pack with the pointy end up. and for guns with a pistol grip you would orient the grip in an up down direction and the barrel would fall along the x axis for instance.