bookshelf for tv?

To meet your requirements neither would be the best choice.
Problem is that most TVs only have fixed audio outputs so adding a subwoofer later is a problem, Also powered speakers don't usually have their own remote control (unlike sound bars). So you don't have a way to control the volume of the speakers and sub at the same time. Not practical IMO.
Soundbars don't usually have a way to add a subwoofer later unless you can find one with a subwoofer output on it that doesn't come with a subwoofer in the box.
You could get a surround sound receiver (new or used).or a 2 channel amp like this one
http/www.parts-express.com/smsl-q5-pro-stereo-amplifier-usb-optical-coaxial-dac-with-subwoofer-output-2x40w--230-210
and a pair of passive bookshelf speakers.
Good quality speakers will give you clarity at low volumes. Used ones would be an option. You can add any subwoofer later since the amp or receiver will have a subwoofer output. If you go with the receiver you could add a center channel for dialogue which will give you more low volume clarity. Surround speakers if you want later.
You should be able to find a used non-HDMI input receiver pretty cheap. It just needs an optical digital input.