If I receive a transaction from four different people at the same time, are these transactions going to be received by different nodes?
It's not that each transaction goes to a mempool of different node.
Once you broadcast a transaction, it's propagated to the network and almost all nodes will receive that. If you received four transactions, almost all nodes will probably receive all those four transaction.
So, in my opinion, mining nodes will include them in various blocks, and their hash rate and nonce will differ.
Miners prioritize transactions based on their fee rate and it's possible that a miner include all those four transactions in the same block.
Is it normal for bitcoin transactions to result in blocks that include completely varied orders of transactions that were generated by various nodes?
Again, transactions are prioritize based on their fee rate.
Assuming the fee rate of transaction A is higher than the fee rate of transaction B, transaction A will be probably confirmed in the same block than transaction B or earlier.
Once a transaction is broadcasted it is received by each nodes and they create a candidate block and add this transactions into the candidate in order they see fit,
Not all nodes need to create a candidate block. Only mining pools and those who mine solo make candidate block.
