MTR Monthly Pass

I don't know if this is a stupid question but long story short, to save up money I think I need to get to get a monthly pass to and from work from the MTR. (I honestly want to take the bus to and from work but we only have Citybus near me so I think it would cost more? *Correct me if I am wrong. It is also my first time applying for a monthly pass*)

I work in Central but I live in Yuen Long. I asked an MTR staff what the difference is between the Tuen Mun - Nam Cheong Pass ($545) and the Tuen Mun - Hung Hom Line ($635) in terms of how I will be charged since I will be coming in and out of Central station and not Hong Kong Station. He told me the Tuen Mun - Hung Hom Pass is cheaper despite it being $635 which to be honest I don't quite understand and had trouble understanding his explanation. Is this correct and should I be following this?

If you have any tips on how I can save up money and honestly making my commute not energy consuming, please do share! It's my first time working in Central and I just moved to Yuen Long. Thank you.