On your splits it all depends on the liquidity versus return as it depends on the markets and if your split is because of liquidity

Lump sum and DCA are subjective because it can be only calculated based on the executed buy order. There isn’t no compounded interest only unrealised gains or loss subject to market valuation. It is not fixed as markets can go down hence your portfolio is down.

The only projected returns is to use goal based investing to set the targets

Remember Past performance doesn’t reflects future returns as it can be higher or lower all depends on markets 

buying and selling unit trust and equity based assets do not generate returns like interest. That term is used for loans / liability / deposits. So, yes, when you decided to sell, you calculate the amount you have put in (tally up vs time) and the selling price and calculate the returns / gains. That is when you realise the gains or losses.

In between, some of the assets you own will generate returns in cash and will be given back to you in your total holdings, reinvested (in the case of Stashaway non-simple).

At anytime in between, it can be negative (worth less than you paid for) or worth a lot more than what you sell it for eventually.

You will know the actual returns at any time of the day, if you decide to sell then it is more or less at that price (+ daily actual fluctuations, + exchange rate charges). It is almost 99% accurate.