What apps are supported and safe on Android 7.0?

LG G Pad X 8.0 running Android 7.0, security patch level April 1, 2018. Just dug out this old tablet that a friend gave to me and looking to repurpose it into something useful. I’m used to Apple devices. I looked in the Play store and it looks like I can download any app I’m interested in. But is that safe? Are these older unsupported app versions with security risks? Is there certain apps that I should avoid using on this for security reasons? Is Gmail safe to use? What about Chrome browser? I’ve got Firefox with UBlock installed, maybe that’s better to use?