color – What accessibility standard for mobile applications?

The W3C has created accessibility guidelines for websites. A is the least accessible and puts the least restrictions on the design, AAA is the most accessible and places the greatest restrictions on the design. W3C recommends that accessibility standards be applied to content other than the website (Source).

I design a mobile application for iOS and Android and I would like to choose an accessibility standard. My team and I are debating whether AA or AAA they are better. This will have a direct impact on design decisions, for example, the choice of color. WCAGs contain minimal contrast ratios between the text and the background color.

On the one hand, we want to be as accessible and as best as possible in the future, which speaks of AAA. On the other hand, both Android and iOS come with accessibility features, which dramatically improve accessibility regardless of our color choice, so AA might be enough. For example, Android has a function to increase the size of the text.

Is it okay to say that AA is good enough, because users can increase text size with the built-in Android tool, which makes a lower contrast acceptable?

My question is about this specific example (color contrast), but also about a broader approach: can we be less strict about design options, assuming that the accessibility features of the operating system will improve accessibility for those who want it? Do you need?