It is advisable to keep your private key or phrase in hardware wallet or some offline storage system as keeping these detail in phone will be a stupid decision. Talking about crypto related app , always enable 2fa and pin security option so it will difficult for another party to look inside your app and do not install these miner or false looking apps or do not give access to them.
If you are using crypto wallets on your phone, it is advisable that you do not install lot of unwanted apps. Only install the required apps and never install directly from .apk untrusted sources. Also it is more secure to use iOS than Android as iphones are more secure than any android phones.
I agree to this sentiment which IOS is more secure than Android but it doesnt mean that it would be 100%.For now then this would be a considerable choice.
https://www.sophos.com/en-us/security-news-trends/security-trends/malware-goes-mobile.aspxLets go on topic reply on how to protect my phone if someone do search? They cant easily get it from you but once government is the one
who would request then you wont have any choice but if you know on how to secure and hide things up then you shouldnt worry.
the reason why ios is more secure because its too strict ,you cant easily install anything but you can only easily install something that is already on the appstore . ios is also a closed source right ? i heard before but android is an open source platform which is its less strict. anything can penetrate on your phone . hiding your info inside your phone would still be useless if there are already viruses inside it