Have some academic questions about Bitcoin mining

My understanding is that the one “winning” miner who validated a block will be rewarded with both the block reward and transaction fee. Does that mean all the other miners do not receive anything from their efforts to mine that block? I’m just wondering how individuals would make anything at all from mining unless they joined a huge pool. Furthermore, do miners pick and choose which transactions they will include in any block? In other words, are there blocks comprised of different transactions that are being mined at the same time in a race for validation? What happens to the transactions in blocks that don’t get validated at that time? Back to mempool? Just trying to dig deep here to really understand mining. I appreciate any info!