Personally, I would go much bigger than 100g for a fully grown pleco, but if 100g is what you can reasonably afford and fit into your home, then it's still better than a 55g.
Something that helps with skittish fish is having more hiding spots. They will be more brave if they know there's a few places they can run and hide to at any moment.
Something that helps with skittish fish is having more hiding spots. They will be more brave if they know there's a few places they can run and hide to at any moment.