Specifically, I began optimizing ways to conserve time and make New Game+ a bit more of a breeze. If you're planning on replaying the game, I'll give you a few tips to make your replay easier to pace through. However, I'll start with one thing every player should at least consider if they didn't make it their first run.
Play the Golden Deer route
For starters, whether you've played through Crimson Flower or Azure Moon, your run isn't over. When I finished Azure Moon, I was left with a sense of completion. I was glad that I avenged Dimitri and closed the book on his story. Despite this, we saw the faction - Those Who Slither in the Dark - appear earlier in Part 1. Who were these mysterious people and why weren't they addressed in Part II?
Verdant Wind not only explains who they are, but also uncovers the truth about Rhea and Nemesis. It sheds more light on the overarching story of Fodlan including several new maps and music as well. Importantly, Verdant Wind also solves the underlying threat not present in my first route. Rather than focusing on Edelgard and Dimitri's personal struggles, this brings the continent's underlying struggle and brings it together full circle.
Video courtesy of LetsPlayGreatGames
Skip the Auxiliary Battles
If you've done them once, why do them again? Outside of fulfilling some Paralogue chapters, there's no point in draining your activity points in Battles outside of a little EXP and skill points. You'll gain both in spades through chapter battles anyway. If you're playing on Normal or Hard mode, you can carry yourself using your Renown.
However, if you're playing on Maddening, you might want to consider level grinding after all. The choice is yours. If you decide to play through it, you might benefit from reading a guide first. But if you're not willing to play this mode, you can focus more on the story progression without adding extra battles on top of it.
Allocate your Renown Points
Speaking of Renown, make sure you use it wisely. Start with maxing out Professor Level so you gain access to all the Monastery activities. Then use the rest to max out the Saint Statues. After that, I would recommend maxing out classes, like Byleth's Myrmidon, so you're not just grinding them for points.
Level your weapons up to C so you can save renown to upgrade them afterwards. Also, keep in mind that anyone you're recruiting from other houses, which you used from a past run, is eligible for upgrades as well.
Optimize Activity Points in the Monastery
Unless you're really bent on hearing what everyone has to say once again, use your points and your time wisely. Use up points in the Dining Hall to increase unit motivation or give them flowers if you run out of Activity Points. If you're keeping Byleth in his special class, and you've already reached high rank for his weapon levels, there's no reason to train with your allies.
You can also feed animals for forge materials or visit the Abyss to trade renown for special weapons and items. Otherwise, you can just grind Dining Hall meals and call it a day. Hopefully these quick tasks will simplify the overwhelming notion of exploring the Monastery roughly 30 times per playthrough.
Alternatively, if you're feeling really confident or overleveled, you can always spend time resting or doing Seminars for skill growths. Rest will also re-motivate your students up halfway.
Play the Cindered Shadows DLC
If you're interested in spending $24.99, you can grab the Expansion Pass. This content features 10 hours of additional content featuring the Cindered Shadows storyline. You'll meet four new allies and gain additional classes and Paralogues. You only have to clear it once for your new units to appear on any route you play on. The new classes will help benefit some characters outside of the Ashen Wolves. For instance, you can make Flayn a Dark Flier to aid her movement and allow her to continue using magic.
In addition to the bonuses you'll carry out of the DLC, you'll also get one of the highlights of Fire Emblem's storytelling. Even if you've cleared the game once, this campaign is worth playing through and the bonuses you get warrant that second playthrough. With that said, the Cindered Shadows run delivers in full.
During Part I, the maps and storyline won''t change. The most change you will get includes the dialogue spoken from your house members during meetings. You'll also gain side-quests for some characters in order to obtain a sacred relic.
Otherwise, if I'm being honest here, you may find little reason to explore during Part I except for quick boosts to stats and EXP. Some people may find themselves feeling burned out from replaying the game due to the first arc's symmetry in all routes. Part II changes the story completely.
Unfortunately, the developers did not add an option where you could skip right to it. Even with pre-classed units, this might have saved many players a hassle. Ultimately, this is probably the biggest flaw involving the game's replayability.
If you're invested in learning all the stories, then I recommend you follow the aforementioned steps. Optimize your weapon levels, class skills, and use renown for quick boosts so you don't have to grind levels in needless battles. If you enjoy playing Fire Emblem, and don't want to watch all the scenes on YouTube, I recommend playing it again. Hopefully this guide will provide everything you need to make your next run a little smoother.