--snip--
and if you want to burn the coins transfer them to the genesis block
IIRC only UTXO created by genesis block can't be spend, where other Bitcoin send to P2PK address (used to mine genesis block) can be spend.
If you were to suggest the best coin that should be merge-mined by the miners, which coin would that be?
Technically miners should be able to mine multiple merge mined coins at the same time, they don't have to choose only one.
But from a profitability perspective they'll have to check the market and see which coin has a higher value (or is being pumped at the time) that can give them higher fiat reward when sold.
From a utility perspective, the projects have to analyzed individually but if I wanted to choose only one I'd go with RootStock since it is a decent project and I believe side-chains are the better option that can satisfy everyone in this context (ie. provides additional revenue for the miner whilst has additional smart contract capabilities capable of creating
real tokens).
For additional reference,
1. F2Pool homepage state they perform merge mining with HTR, ELA, NMC and FB.
2. Antppool homepage state they perform merge mining with NMC and FB.
But looking at their mined block, they also perform merge mining with RSK, exSat and other stuff i don't recognize.