You can definitely change some of those settings, but I think mobile resolution is very picky. You can’t change resolution on the fly, and there is no Screen Percentage option for post processing.
I have successfully changed AA quality with r.postprocessaaquality" being typed into the console command, as well as r.bloomquality, and maybe a couple other random ones.
Also keep in mind that you can use the Device Profiles to alter some rendering settings based on phones. I know you can do it through the editor, but I’ve had better results going straight to the BaseDeviceProfiles.ini in the Engine configs. Here, you can set a lot of console variables, including MobileContentScaleFactor, which is the resolution. I believe the only reliable numbers are 1 and .5, but I’ve heard that Android phones can also do something like .75. So if your client has a low-end phone (as judged by something I don’t know about in UE4), you can do some of the work for them, while keeping awesome settings for the latest GPUs.