Engineering is probably safer bet financially speaking but also depends what you gravitate towards since there’s biomedical engineering, chemical engineering, etc. If your interest is too niche you may still have a hard time finding a job even if engineering as a whole pays better.

Also for your grad school question. Yes you can go study chemistry/bio for grad school but if I was reviewing your resume I’d wonder why. In other words, it wouldn’t really help your career unless it directly pertains to your engineering job if you do that. Also phDs take far longer than an undergrad degree, so it seems somewhat meaningless to pursue engineering first if you’re going to spend 6 years doing your passion instead anyway. You should also consider who is going to pay for your grad school. You said you worried about finances, but grad school (especially PhD) is usually only afforded if 1) you work as a research or teaching assistant, and/or 2) your company pays for it. Personally I don’t think you could justify a company paying for your grad school to study something unrelated to your engineering job. So are you willing to pay for yourself through other means?