What is the difference between SHA-1 and SHA-2?
SHA stands for Signature Hashing Algorithm. It's a mathematical hash that proves the authenticity of the certificate. SHA-1 is an older version of the algorithm that is no longer seen as secure by industry experts and major browsers and is not allowed to be used during the generation process any longer by the industry. SHA-2 is the latest version that is widely accepted and viewed as secure by all major browsers and industry experts. The hashing algorithm of your CSR has no relevance to what hashing algorithm is used on the certificate.