This is a good question because you’re asking for relative value of several curricular and extracurricular activities through the eyes of an employer. From now until you get hired in a discipline and job that you really enjoy; your focus should be on making yourself one of the best candidates you can for companies you want to work for where you will be doing what you love. I’m making this fairly obvious point to remind you that most of the people you’ll meet for the rest of your life will be trying to sell you something, and that includes most colleges and universities. Get the education that companies want you to have, not necessarily the one universities want to sell you.
In that vein, I assume that your use of the words “relatively easy” to describe a major in ChE with a minor or double major in math or biochemistry came from a course catalog where you noticed how close to a minor in math or biochemistry you would be if you majored in ChE. Am I correct? If not, sorry. I noticed it when I was in your shoes. I just wanted to assure you that just a major in ChE will keep you busy. As far as school clubs, unless you’re Pres or VP of university, engineering, or ChE honor societies, I don’t think it will help. But use your own judgment as you’re looking through the eyes of an employer.
In my 35 years as a mechanical engineer including three short term assignments in college recruiting, I have been told and discovered for myself that the most important thing company recruiters are looking for, aside from your primary degree, is work experience related to that degree. That work could be from a job you found (as long as it’s pretty close to what you’d be doing if hired - that’s what I did) or from an internship from a company.
In my opinion, a minor or double major is generally not what potential employers are looking for. It’s difficult to make such a broad interpretation, but at least for engineering I think it’s safe to say. It depends on what you want to do of course, but unless you want to work on proving and disproving mathematical equations used by ChEs then having a minor or double major in math doesn’t really help. For biochemistry it’s the same question, but since it and ChE are somewhat related, if you want to work on projects where the two fields clearly overlap, it might be advantageous to do a minor or double major in biochemistry.
Here is the calculus. Your most important degree is ChE, so as long as you get good grades in every required class for a ChE degree, you can use your electives mostly on math or biochemistry as you like. If you need a few more classes to qualify for your minor and you take them, then you’re done. Now do your cost/benefit analysis---was it worth it? For a double major with ChE as primary, after you take all your required ChE classes and use some of your electives towards your second major, I am guessing but I would think you would be looking at another year of school. Now do your cost/benefit analysis---was it worth it? For purposes of argument, let’s say that your second major required that you stayed one more year. So, you went to school for five years and you have two Bachelor’s degrees. If you have the time and money for one more year, you can have a Masters degree. Now do your cost/benefit analysis again. OK? I would argue that a Masters in ChE, or a Bachelor’s in ChE and a Masters in biochemistry will stand you in better stead with potential employers. But you have to want to, really bad. Best of luck.