There's no need to delete your old apps just to get those apps updates. When you download the updates..it will be written over the old apps. So the app size roughly still the same before and after the updates.

Let the media scanner do its job first...scanning all your media and cache all the thumbnails. Once it finished scanning..it won't wake your phone anymore.

If you reboot or clear ram/cache...your media scanner need to start it works all over again.
Result : more wakelocks..more scanning..use more battery and time wasting to build those thumbnails again.