Is there a way to see app being used and text on my acct

No to both. Your account data log only shows how much data is used, not what uses it and your text log only shows date, time and number, not the text content.

Is there a way to actually SEE what app is being used

On the phone itself, yes.  In settings, data usage. 

or SEE what someone has texted (to/from) on my account?

No.  Text content is only on the phone.  It's private communication.  AT&T has logs only, no content

Data usage on the phone will specify what app is using how much data.

You cannot see what someone is texting, just like you cannot hear their phone conversation. That is private communication. To see the text messages, you would need the actual phone itself to look at them (if they are not deleted).

Sorry but being the account owner does not give you rights to someone's private communication.