If we're talking about native mobile apps, load times & number of pages normally don't apply. Hybrid apps, on the other hand, might have some of those ideas.
Dynatrace gives you several options, both with RUM & server side monitoring. With native apps your best option for RUM is instrumenting it with a SDK.
I believe there are no "industry standards" that apply.
Recommendations, there are many, but more for web apps, or hybrid apps that use web pages. Probably the best is to adhere to recommendations done by Google, as they can affect aspects like revenue and SEO. If monitoring with Dynatrace, I would try to keep Apdex as high as possible, and errors/crashes as low as possible.