Lock password required after some time of not using it
All  of what you need can be done on Native android; No apps or root required. Go into your settings, Display, and Set 'Sleep' To 30 Minutes of inactivity.

Then, go into the Lock screen/security settings, and untick 'Power button instantly locks device'

Now, even though hitting the power button turns the screen off, it won't lock, and if you leave the phone to it, it will lock and turn off after 30 mins.

As Ethan Said, you can also adjust how long after the screen turning off the phone locks, then just disable lock on power button as before.