You mentioned connecting dozens of nodes here. Do I need to fill in these node addresses in the Bitcoind.conf configuration file? Or fill in many node addresses in my code? Thank you very much, I am a enthusiast who just participated in learning blockchain
In Bitcoin.conf file, you should be able to add as many nodes as you want but there will be a restriction on the number of nodes your client will connect to. You can try opening port 8333 to allow other nodes to connect to you, the node count should increase gradually as your IP address gets relayed and propagated through addr messages within nodes.
Generally, the transactions that are non-standard, ie. valid transactions but are do not pass the standardness check[1] enforced by the nodes, will not be accepted by your node. They could still be accepted into a block however. Those are the kinds of transactions that you'll probably never see in the mempool, but only in blocks mined by miners.
By attempting to connect to as many node as possible, you could allow your bitcoind to potentially have more sources for the transactions to be relayed to you, deceasing the chances of certain transactions having low propagation (Txes with low relay fee, etc) but are otherwise standard and valid.
[1]
https://github.com/bitcoin/bitcoin/blob/master/src/consensus/validation.h#L21