I was a fan of the Harry Potter books long before I even read Lord of the Rings.
Anyway - even though the similarities are definitely there, JK Rowling has stated in interviews that she has never even read Lord of the Rings (though she might have by now). Assuming that she is not lying - and why would she? -, how did those parallels come into being? It seems as if Tolkien and Rowling were perhaps both inspired by the same source and the books are more like siblings than father and child, if this rather strange metaphor makes sense. Maybe it’s also interesting to figure out where the books are clearly different. For example, Harry Potter completely lacks religious influences and is set in a relatively modern world - a world that does not always take itself so seriously as Tolkien‘s Middle Earth.
And Snape? He’s definitely a good guy at heart. Oh yes. I’m a fan. He's nothing like Grima. Wormtail is Gríma.