I think happiness IS subjective, as stated. I know many who are truly happy working extremely hard. Yes, they may stress, but overall, they love themselves/their lives better when they are working hard and seeing those results.
I know others who really are minimalist and prefer not to work too hard and take it easy.
I don’t believe there is any right/wrong answer, as long as you’re not hurting anyone. Although I do think it’s important to be self-sufficient to some degree and you shouldn’t freeload (ie “It would make me happy to never pay bills for anything” is not good because you burden others), if you TRULY want to take a job where you don’t have to do much, where you can have lots of free time and take it easy, do it. If you want to work hard and dedicate your life to something, do it.
I think for most, there is balance. Few are completely one extreme to the other.
I know for me, I love to work hard but I also like to enjoy myself in my free time. I don’t mind replying and checking my work email when I’m at home (and I’m hourly, I don’t get paid for that, don’t care) but my free time is of very high quality and I am happy with that.
I strive to work hard and to have a relaxing, enjoyable leisure time. To me, that means not having children (Kids stress me out, don’t enjoy being around them), living in a quiet place so I can get good sleep, going to a gym, and seeing my family/friends when I desire.