I have noticed that with 100 % there is no big difference in printing time or material consumption but the enclosure prints truly sturdy.
Also to get the bottom surface smooth use 35% infill density, "line" support type, 0 gap between support and above layer. To ensure the line type support stays on the print-bed surface, I use 5 loops of brim which is at 0mm distance from the part (in our case from the support structure). When I print with PLA I use heated to 65℃ BuildTak covered print-bed.
Use "Touch Platform Only" support setting.