More decentralized? I have not stated this. I have stated that LN is decentralized and secure which is correct; you can't be the judge of this because you don't have a technical background as you've said, right? If anything Bitcoin will be very centralized if we focus on scaling via the block size. You can't deny this.
No. As I have pointed out to you before, with SegWit, all nodes that want to operate in a trustless manner require processing the signature chain as well as the 'blockchain-minus'. There is NO efficiency gain for a node operating in a trustless manner. What you call 'efficiency gain of SegWit' is only achievable by nodes that must trust other nodes to perform validation for them.
As such, SegWit does nothing for the centralization issue.