For your second question. I changed the highlight color to a light grey. You could change it to be the same as your background color to make it "disappear", but the idea is to highlight the SQL statement you ran if there are multiple ones. The is in Preferences under "Program Window" then "Hot Track Highlighting".

One big difference back when I switched from TOAD is that TOAD has one editor for everything (or at least it used to) and PL/SQL Developer has different ones for different tasks.