Why do 1080p movies have a resolution of 1920×800/808 instead of 1920×1080?
Blu-rays are 1920x1080p but usually include black bars in the video, the rippers/encoders remove this when they make smaller encodes to save space I guess. There’s really no way to remove the black bars on such movies without cutting off the sides.
Can I get fined for browsing torrent sites?
In most countries, no. You’re also safer if the site uses TLS (https).