I found this Brazilian YouTube channel that's talk a lot about SpriteKit, maybe it's a good starting point https://www.youtube.com/watch?v=zoUwIH7g-wY&t=363s (This video link is a playlist about creating from scratch a game using SpriteKit)

In fact, I have a slight impression that perhaps the TileMapNode is configured with a different Tile size than the asset size. Because it seems to me that it's not fitting into the grid Can you check if the TileMapNode is the right size?

The Frame you are talking about is PhysicBody, right? If so, it's because when you change the texture, even though it asks you to resize, it doesn't change the physicsBody, so you would have to recalculate