Hello Crinity,
Some of what you are asking to control, is already handled when you deploy to different devices that cannot support HDR. This will effectively disable any settings or features that are not supported by HDR. Creating device profiles, and understanding which settings within Post Processing that are improving performance when disabled. Honestly, I would take a look at the documentation we have on Post Process Effect on Mobile as well as our Mobile Development information to help you understand why disabling the entire tonemapper is not something that is recommended as Mobile post-processing is handled differently than PC.
Post Process Effect on Mobile
Setting Device Profiles
If you have further questions or need additional assistance, please let me know.
Thanks,