You should only take out parental leave 7 days a week if you need the money right now. Taking 5 days a week will enable you to spend more time with your kid at home, send them to preschool at an older age, and/or save up some days for when they're older (e.g. so you can take longer vacations together).
When planning parental leave, it's good to know about SGI, or 'sickness benefit qualifying income'. This income is the base in calculating how much sickness benefits and parental leave benefits you receive. SGI is calculated based on your salary before your parental leave. More info here: https://www.forsakringskassan.se/english/moving-to-working-studying-or-newly-arrived-in-sweden/social-insurance-system/sickness-benefit-qualifying-income
In general, your SGI gets reduced if you stop working or reduce your working hours (e.g. work part time after your child is born) - unless you 'secure' it. Regardless of what you do, your SGI is secured until your child turns 1. This means that until their first birthday, you can request parental leave from your work without taking out parental benefit, and your SGI will not change - this will allow you to save all the parental benefit for later. Things get more difficult after your child turns 1 - you have to work, receive parental benefit or sickness benefit, and/or be registered as unemployed for a total of 40 hours a week. Basically, these activities need to sum up to full time. So you can e.g. work full time, or be on parental leave full time, or work 50% and be on PAID parental leave 50%, etc. and your SGI won't be affected.