LLL: Long Live Lucio!
Accelerando is my talent of choice for 90% of games. This has traditionally been the only choice at this tier since release. It massively increases Lucio's slipperiness, allowing him to dodge telegraphed abilities, chase enemies, and generally be a nuisance.
Smooth Moves is an intriguing choice with some niche use cases, however. The mana regeneration from auto attacks procs off everything, including minion waves, making it a great choice to combat Lucio's mana-hungry E button. That said, the heal is not worth the trade-off of losing the bonus movement speed from Accelerando. It's a cool concept, but I would really only recommend this talent to people uncomfortable making use of Wall Ride.
Off the Wall is absolutely the only choice at this tier. Please don't pick anything else.
Smooth Moves was a surprisingly refreshing talent to see in Lucio's tree post-rework. The modest shield gained from hitting enemy heroes with your Q is enough to make it the most lucrative choice at this tier, allowing you to more effectively dual and out-trade people.
Boombox remains a solid alternative for anybody who would find the gained vision radius more useful than extra survivability.
RIP Reverse Amp, Sound Barrier reigns supreme as the top shelf ultimate this patch. Make sure to wait out enemy CC before casting this ability and then move into range of teammates as enemy heroes are using their ultimates. An interrupted sound barrier is a one-way ticket to a lost team fight (and yes, it is your fault).
High Five is no pushover, this talent is super solid against comps with single target burst. Think heroes like Varian 1H, Kel'Thuzad, or heroes with targeted ultimates like Sylvanas (Mind Control) and Chromie (Temporal Loop).
All Together and Slip are both fine choices at this tier. If you need to dodge skill shots, go for All Together. If you're more concerned about point-and-click abilities like auto-attacks or things like Diablo wall slams, pick up Slip.
Up The Frequency gives us the highest potential aura uptime of any talent. You should be able to consistently auto-attack with the safety granted via Accelerando and All Together/Slip. Just be wary of the mana cost of Amp It Up. It might be tempting to amp speed boost whenever available, but it is generally smarter to play more conservative and wait until you can amp up a heal that grants value to your entire team.
Rejuvenescensia is still OK, but its a less appealing choice after the nerfs. If your team is super tanky and you absolutely need the burst healing, this talent is probably fine.
House Party is no Bonus Track, but its healing increase is still incredibly powerful. Plus, the rest of the talents on this tier are fairly gimmicky.