To recharge batteries, sine wave is irrelevant. For lights, I'd suggest getting 12VDC lights if you can, so you don't have to power an inverter to run 120VAC lights; or get rechargeable lights you can plug into the solar unit during the day.

Check this page and see if it answers your questions on sine waves:
http://www.donrowe.com/inverters/inverter_faq.html
(With regard to powering laptops, note that recharging the battery is different from running the laptop off the inverter.)