Hey, from personal experience "Metamorph" isn't really a thing were you can put all your points into but you can have it mixed with something else as you said above. If you want to use a spear and a bow I would recommend starting off putting one point into scoundrel (or warfare or huntsman for weapons if you want) for adrenaline and one point into metamorph.. I would then as put points into finesse during character creation and maybe put a point into wits or con to if you want. From there I would get adrenaline, chicken claw, and tentacle lash. From here I would start off the game and work my way getting the darling bow from the dig spot near the entrance of fort joy and get the spear of braccus rex. From here I would get chameleon cloak and try to make your way up to heart of steel, wings, and whatever you want (medusa, oily blob, etc). This is how I would make my character but you can do what you want.