Since The Sims 4’s new update on 9th of September, 2014, you can disable that white outline that appears each time you hover over an object or a Sim.
To do so, open up your Cheat box using Ctrl + Shift + C and enter hovereffects off. (hovereffects on if you want to turn it on again)
Please note that this won’t apply to the white outline when you click on an object/Sim.
If you don’t like turning on this cheat each time you load up your saved game or travel between lots, you can make it apply for good using Command Lines on Origin.
To do so, open your Games Library, right click on The Sims 4 box and select ”Game Properties”. Add -nohovereffects in the Command Line Arguments section. If you already have a previous command written, just add space and add a new one.