Hi people, should I open an epf account or get the account number before starting to work (fresh grad)? Or do I have to wait till I've started working?

You can leave those blank.
Company only need it /address when you are employed.

EPF is employee provident fund = mainly savings for retirement.
SOCSO is worker's insurance = payout in case worker accident at work / to-and-from work.
EPF is deducted from workers salary and contribution by employer based on % of salary.

If full time employment, HR usually register these for you.
If contract or part time, some companies may omit this.
I cannot say I agree but salary more important.

When you get your payslip, ask your HR how to identify you income tax LHDN number.
If the register for you, then if you fall into income tax deductable bracket, then you have to declare yourself by April.
If not, then nothing.

Around March, you can go to EPF office request for your EPF annual statement last year, see who contribute and how much.