For the POS to work do we need to keep coins stationary in our wallet for 30 days, or can we add/remove coins from our wallet in the 30 day period?
The funds must remain stationary for at least 30 days. By unlocking your wallet (necessary for minting PoS stake reward/interest) every 30 days, you will earn interest of 1.2% annually on your holdings. If you unlock your wallet every 90 days, you will earn 1.5% annually on your holdings. So it is recommended to take the easier route of every 90 days and earn max interest.