Here's an old picture of Solveig just after I glued in her magnets. You can see the proportions of the wood style antlers/horns pretty well here:
The twig horns are much bulkier by comparison, so I think whether or not they'll work for you will depend on how/where you position them on your doll's head and if you like the overall largeness of them.
As for clothes, these girls have a tendency to look like they're wearing a potato sack if you're not careful. Their chests are so much smaller than their hips that generally to accommodate their lower half, the upper half of the outfit will be too large. If you can, I'd recommend finding or making something that really comes in at the waist, or that you can pin in the back to make sure that you keep her upper half defined.