What's different about Deco Mesh?

Hi, I'm exploring at the possibilities of installing mesh system in my house and im strongly considering deco mesh system.

However, i just realized that my current TP link router + tp link routers that ive set as AP also have easy mesh system. I'm wondering, what are the differences between the two mesh system and is it worth the upgrade? I'm going to utilize the ethernet backhaul even if I buy the deco, so the ability for a wireless backhaul is kinda useless to me.

side question: I also have an old TP Link AC1200 router (archer C5, firmware: 3.13.34). This doesn't have the easy mesh option. Is it possible to add an easymesh feature to this router, by upgrading the firmware for example? or is it not possible due to the outdated hardware.