There are three things you can check when you're trying to determine if an app is safe for your Android device:
Check the app permissions and look for anything suspicious. If it says access photos, videos and files stored on your phone, be wary of this kind of requested permission since apps that need these kinds of permissions usually aim to steal important data from users.
Look at information about the developer or creator of the app such as his name and email address. This will help you know more about who created the modded files you're downloading so you can get a better picture whether they are legit or not. Also, see if the legitimacy claims are coming from real people or just computer-generated statements that can be faked easily then decide if you really want to install the app on your device or not.
Check other apps similar to this modded file that you're downloading. This will help give you an idea of whether the mods are safe to use or not, especially if it's already popular among players. It is also good to check forums and other websites where you can get detailed information about these kinds of APKs before downloading them onto your device.