If you are going for something exactly like PUBG with no wiggle room, adjust your LODs so that your meshes become even more simple (like with the tower and trees), and use textures that can be scaled down more easily/more simple/smaller textures than you care currently using. Optimizing Mipmaps and LODs will be your best bet for mobile optimization. Here are some great non Epic guides for optimization:
I hope the above solution works for you!