We recommend a map resolution of 10 meters/pixel in case of having a larger simulation area as it is the case with 2 rings of base stations, since the dimensions of pathloss map will increase ant that can consume a lot of RAM. However that depends on the actual machine you are running simulations. You won’t do a mistake by choosing between 5 and 10 meters/pixel. The smaller the map resolution, more accurate calculation of the large scale losses is, however that goes in the expense of RAM resources. It is a trade off that you decide how to cope with.