I had an anterior placenta with DS1 - it is nothing to worry about at all - a large percentage of placentas are anterior and it is of no risk or issue at all. the placenta just masks the feeling of movements and bub is hitting into the placenta... so you cant feel as much. so dont be worried if the mvts are lighter feeling and you dont feel them til later.
I dont know re the low laying placenta - i didnt have this but it is not related to anterior placenta as far as i know. i am sure others will have info as this is also reasonably common.
Enjoy your pregnancy!