Pixel problem of making outdoor community recruitment posters in PS

1, the size is 708*246mm. This is not a regular poster size, but a bar banner. Please remind me here.

2. When creating a new file, select "mm" as the unit of width and height. Because it is outdoor publicity, printing and poster spraying are not needed, and the highest resolution is 150dpi. If the computer configuration is not high, you can also use 100dpi and 72dpi. You don't need 300 resolution, otherwise the computer drawing will be very stuck at this size. As shown in the figure below:

You can see the pixel size below. The higher the resolution, the larger the pixel value, and the more stuck the computer. So just choose enough.