You have some control over when you start taking your distributions at retirement. The 401k rules stipulate certain dates that you must follow, but the flexibility comes in between 59 ½ and 70 ½. To avoid unnecessary taxation and penalties it is recommended that you start distribution after age 59 ½.
You do not have control over the investment platform offered within the 401k plan. The employer and/or plan sponsor works with their financial advisor to select the investment funds within the 401k plan. It is the fiduciary responsibility of the employer/plan sponsor to select funds for the 401k plan that are well diversified and cover all asset classes. So plan sponsors have to be very careful when they make their fund selections for the 401k plan.
You as a participant also do not control the rules within your 401k plan. 401k plan rules are set by the Internal Revenue Service (IRS) and the Department of Labor (DOL). These 401k plan rules include contribution limits, distribution rules and loan rules, for example. There are many, many more rules which you can locate on the DOL website.
You do not control the vesting schedule set up within your 401k plan. Your employer determines the vesting schedule.