within 'Principal', there are Save and Invest, where multiple funds are available
so assuming u r referring to mmf for comparison purpose
the key difference is liquidity, u won't be able to access the money in the 'Principal' instantly like Go+
they are invested in different underlying fund
Go+ distribution policy is daily, so the interest is 'paid out' daily
GoInvest Save does not distribute daily but the interest 'earned' daily will be accumulated in the NAV, so u would still receive the accumulated interest when u sell