Archviz for Ios has low Fps

Hey guys, iam working on a archviz for Ios platform and currently using ipad2 for testing. I have found that frame rate is not doing good after packaging the project. Is there any way to improve the Fps while holding the quality of the project. And there is metal render and forward shading in the Ios setting… What is the difference.
​​​​​​Because when I done use mobile render the whole project starts to flicker you can’t even see where are you going.
Please help?