Question about above ground pool vac and pool pump timer from newbie.

Hi! I'm new to the pool scene. We have a 21 ft above ground pool. There are two things I'm considering buying for our pool. An auto pool vac and a timer for our pump. Are these worthwhile? Are there any brands to shy away from for the vac? I'm looking for a reasonably priced one and would prefer to keep it under $150.
As for the auto timer, our pump has two speeds. We are leaving for FL soon for a week and I'm not sure what the best thing to do with the pump while we're gone. Since we have a two speed pump, am I correct in saying that if we run it on low it should be 24/7 and if it's on high 10-12 hrs? My husband kept putting it on low just for the day and I kept telling him that's defeating the purpose. If I go with a timer is it better to get a plug in or one that is wired in?
Thank you very much.