First, you need to know that users don't pay for security and transaction fees are not set by the node.

Your transaction fees are can by set by your wallet custom depend on how they see congestion of the bitcoin network and you can equally customize it as you want. You can set your transaction to 1 sats/vbytes if you like even if the current network fee is asking for 20 sats/vbytes but the bad side of it is that you will have to wait for when the network become less congested before your transaction can go through. It may not right now, so don't set fees below the asking fees on the chain.

Nodes equally don't set the fees, basically what they do is they receive transaction when you broadcast it to the bitcoin network, they verify the transaction and relay it to other nodes (both mining node and full node) in their mempool and then mining nodes pick this your transaction and include it  to get verify. Once a node verify your transaction, then it becomes permanent in the bitcoin ledger.