Optional Relay Nodes - P2P gossiping: How does the optionality work?

Hello everyone!
I’d like to understand better a couple of things about this post.
If nodes work at different speed (nodes that communicate with relays vs those who don’t) how does this impact the network performances, will it affect round times?
If not, what would be the benefit of relays over p2p? MEV through latency advantages in the mempool?
Does the gossiping lead to increased requirements for nodes?

Thank you for your time :pray: