I’ve read some articles about miners processing transaction once BTC is fully mined, will this happen in the current pool setup ie antpool/slush pool or do miners connect to something different
Miners process bitcoin transactions after the genesis block because bitcoin network is a Proof-of-work network. It will be a dead network if no miner is mining bitcoin.
When the block rewards fall to very low and after all bitcoin in total supply is mined, miners will only do their main work: verify and confirm transactions. They will receive rewards from transaction fees, not from bitcoin block rewards as of now.
In 2140, how much does one bitcoin cost? How much does 1 thousand of satoshis cost? Even thousand of satoshis will be a big money for miners. They won't need to get block rewards in 2140 to pay their power bills.