All three options give you a legal backup if you own the original game, and they are significantly smaller than the HD PC port.
No. Do not download pre-made "686MB" files from random websites. The vast majority contain ransomware, adware, or are broken rips missing essential game data. Download Resident Evil 4 Pc Highly Compressed 686
This is the most significant danger. Many websites that host "Highly Compressed" files use this term as clickbait. Unsuspecting users download a .exe or .rar file expecting a game, only to execute a trojan, keylogger, or ransomware on their system. Because the file size is small (686 MB), users often overlook the fact that a legitimate game should be larger. All three options give you a legal backup