I am thinking about buying Tasker, and swype. If I purchase these apps, will I need to pay for them on each device? Or will a single purchase allow me to install on all my devices?
Apps purchased through Google play store are linked to a Google account and not a device. This means you can purchase an app then use it on devices signed into the Google account that purchased it. https://support.google.com/googleplay/answer/113410?hl=en