Led panel sending and receiving card working
It's entirely up to you.

If you're only ever going to be showing static pictures, then the first option might make sense. The memory increases the cost of the receiving nodes, but the communications bandwidth is greatly reduced.

On the other hand, if you're sometimes going to be showing video, then the second option probably makes the most sense. You need the bandwidth anyway, so keep the node costs as low as possible.

If you want to build a sending card that works with an existing receiving card, then you need to learn from the manufacturer what the required protocol is. Such information may or may not be considered proprietary.