13th Age solves the 5e combat problem by amping up the combat - with HP damage scaling up over the levels (and other mechanics) to make sure combat doesn't bog down. But it will feel like JRPGs in the way that damage and hit points inflate enormously over 10 levels.
The assumptions (class, race etc) are very compatible with your default D&D campaign so converting will be easy. I converted from a 4e campaign to 13th Age with ease. However, some of the narrative rules (Icon system) need some interpretation and work by GM and players to make them work well.
Swords of the Serpentine will probably defocus combat a lot - the resource point-spend mechanics (which I experienced in Night's Black Agents) will make recon, planning, and dirty tricks a lot more powerful, so that often a cunning party can avoid a lot of combat. But the magic system and world assumptions are uniquely Serpentine, and there will be a lot more work to adapt to your existing campaign.
Those are the two top recommendations I have.
Fellowship is also good but may not fit your particular campaign and play group. Read and see.
Savage Worlds is a great toolkit for fantasy adventure, but also needs a lot of work to adapt.
Thanks. Actually, there's an Eberron in Savage Worlds conversion book, so that may be worth checking out.