To see the differences between the two devices, please check out SentinelX BLE vs SentinelX NFC
The COIN app will only provide a bonus for one SentinelX detected, whether that be a SentinelX NFC or SentinelX BLE.
You only need one SentinelX nearby to earn 12X the rewards. Having more than one SentinelX won't multiply the rewards. The COIN App will only connect to one SentinelX at a time!
If you have a premium subscription, you will automatically receive this 12x bonus as well as a 10% boost if you have a physical SentinelX nearby. This boost does not stack with multiple SentinelX's of any type.
If you have extra SentinelX devices that you do not use with your own Geomining, try SentinelX Sharing and have your friends start collecting COIN rewards for you.