BIP 118 is what I would consider as uncontroversial as it gets in regards to softforks.

It breaks nothing and adds a feature for Lightning.

eltoo is an improvement to the Lightning protocol that requires the change provided in BIP 118.

More information on eltoo can be found here and here.

Previous Reddit conversations can be found here and here.

A short summary of eltoo, as "layman" as I can be:

Let's say a "final" state (state 4) of a channel is sent to the network by your nodes peer, but you have a newer "final state" (state 6) and want to contest. To validify your contestation you need to provide the entire history of channel state updates in the transaction.

This is extra data, which cost extra satoshi, and it requires you or any entity watching your channel to store the entire history of channel states.

eltoo allows the freedom to only store the latest state and prove that it's the later state without providing the entire state history.