Autosum feature very different than Excel's

Why does the autosum feature in Calc work so much differently than it does in Excel?

First off, Excel has the very convenient keyboard shortcut "Alt+=" set to the autosum feature, and I cannot find any way to use autosum in Calc other than clicking the button, which is time consuming when you are doing dozens of different sums.

Also, I use my spreadsheets in Excel for digital checkbook registers. In the very first cell, I'll have my current balance. In the cell below it, I'll enter a deposit or a debit amount, and then autosum the two to get my new balance in the third cell. In the fourth cell, I'll type in another deposit/debit and then autosum the result from cell 3 with the result in cell 4, which gives me my new balance in cell 5... and so on. In Excel, I highlight the two cells I want to sum (i.e. cell 3 and cell 4), and when I do the shortcut for autosum (or click the button, which, again, is more time-consuming), and it automatically puts the result in the empty, non-highlighted cell right below the two highlighted cells (cell 5), even if that empty cell has already been formatted/bordered/shaded. In Calc, If I highlight two cells and autosum them, it puts the total all the way at the very bottom of my spreadsheet, right below the last unused cell, which is annoying because I often have pages worth of cells that I've pre-formatted/colored to look like a checkbook register, even though these cells are empty of numerical values. The autosum ignores these empty-yet-formatted cells and puts the total all the way at the very end, which means scrolling through countless empty pages to find it.

So let's say I do things the long way. In Calc, if I select the cell I want the total to appear in (say, cell 5 in my example) and hit the autosum button, it will only blue-border highlight by default the one cell above it (cell 4) and not anything else. To complete the autosum after clicking the button, if I drag the blue-bordered sum-selection field to include only the cell above that (cell 3), then the autosum will give an error because for some reason it has included cells 3-5 in the autosum formula even though I told it to put the result in cell 5 and that cell 5 wasn't even included in the dragged sum range, only cells 3 and 4.

Why does Calc behave like this?