Often, due to their buying power, these platforms access wholesale managed funds, which may have lower fees than retail funds. The platform provider will also charge fees to administer the investor’s portfolio.
Effectively you can have one investment account.
However, you may have many different investments within this account. The platform is what you use to invest through to access the investments.
Take a minute to find your superannuation statement and see if you can establish where and how your monies are invested.