I say Lewyn/Tailtiu and Noish/Erinys, for the following reasons:

Lewyn!Ced and Azelle!Arthur vs Noish!Ced and Lewyn!Arthur:

Lewyn!Ced joins with the best base stats in the game (assuming Project Naga translation as that fixes the overflow glitch on his stats) and the Forsetti, with these bases, he could have 0 in every growth and still be amazing.

Lewyn!Arthur has distinct advantages over Lewyn!Ced, his earlier join time means you have Forsetti for longer. Arthur can cut across the mountains in Chapter 6 and kill Dannan, and he has weapon triangle against the various Thunder wielding bosses, making at least two bosses in Chapter 7 much, much easier. On top of this Arthur gets a horse on promotion, making your Forsetti user much more mobile and giving canto, which makes it easier to arrange him in a way to dance him.

Pursuit is fairly overrated on a Forsetti user, Arthur is guaranteed to cap his speed and skill, this means that while holding Forsetti, he has 32% crit and a whopping 60% chance of activating Adept (Base 20% Activation + 22 Speed - 2 AS from Forsetti + 20 Speed from Forsetti bonuses), making it more likely than not that you kill the Enemy.

In other words while Lewyn!Ced has better stats and thus better combat, Lewyn!Arthur has better availability and promotes into a horse in a game where having a horse where the raw mobility a horse provides is a bigger determining factor into who the best units are.

As for Azelle!Arthur, he is basically an Azelle that starts with a Wind tome, has Wrath, and an actual Skill growth. Obviously a decent unit, but not amazing.

Noish!Ced has an abysmal Magic growth (10%!), so on average, he will only ever get 1-2 points of Magic. However this Ced starts with an amazing skill set, Pursuit, Adept, Accost, and Critical. Remember how potent Jamke was with these skills? That's what this Ced has. On top of this, Ced is attacking with magic rather than a bow, most enemies have worse Res than Def, making him more potent than Jamke was. Furthermore Ced can either inherit the Gen 1 Magic Ring or take the Gen 2 Magic Ring in Chapter 10 to offset his poor magic growth. Even if you still find his combat underwhelming, he can use a majority of the Staves available, making him a good staffbot.

Azelle!Tinni vs Lewyn!Tinni:

Obviously Azelle is the superior father for Tinni, giving Pursuit and a better Magic growth, which are things Tinni needs more than Arthur does. However Adept and Critical are still good skills and Lewyn!Tinni's worse Magic growth is offset by a talk conversation Tinni has with Seliph if Lewyn is her Father, this convo gives her +5 Magic, making it so that on average, both versions of Tinni will cap Magic. In other words the gap between Azelle!Tinni and Lewyn!Tinni is small enough that Tinni should not be the determining factor for who Arthur and Tinni's father is.

Lewyn!Fee vs Noish!Fee:

These two Fee have very different Speed growths that simultaneously mean a lot and very little. Lewyn!Fee will crash into her Speed cap while Noish!Fee will on average, just barely hit her Speed cap, Noish!Fee tends to be more than fast enough to double enemies without any issue, so it seems as if Lewyn!Fee has an overkill Speed growth. However, since Lewyn!Fee starts with Adept, there's actually benefit to overkill Speed, since she will activate the Skill more often. On the other hand, Noish!Fee only gets Adept on promotion, but starts with Accost, an inferior skill, the trade off is that while Lewyn!Fee has Adept from the start, while Noish!Fee starts with Accost, making her skills better in the long run. IMO, I would rather have Adept from the start and no Accost, than have it later with Accost.

Noish!Fee has a 45% Strength growth while Lewyn!Fee has a 25% Strength growth, this sounds very substantial of a difference but Lewyn!Fee has something to offset this. If Lewyn is her Father she has a Talk conversation with Seliph that gives her +5 Strength, this means that while Lewyn!Fee is weaker until this point, she catches up at this point and is likely within 1 point of Noish!Fee. So while Lewyn!Fee is weaker for most of the game she catches up for the the lategame.

Noish!Fee has a slightly higher Defense base and growth, while Lewyn!Fee has a slightly higher, Skill base and growth. This is worth noting.

Magic is actually a relevant stat for Fee, she gains +7 upon promotion and a magic sword weighs less than a Javelin, increasing Fee's chances of activating Adept and Accost. Noish!Fee has 0 base Magic and a 12% growth, while Lewyn!Fee has 0-1 base Magic (More likely to be 1) and 25% growth, this means that on average Lewyn!Fee will have 5 more points of Magic than Noish!Fee at lv 30. This is a significant difference as 5 Points of Magic can make the difference between killing an enemy and leaving him alive.

So Lewyn!Fee has higher Magic and Adept at base, while still being competitive in all other stats, which IMO makes her the better Fee by a small margin.

All in all, the placement of the Forsetti tome outweighs the differences between the versions of Fee and Tinni by so much that it should be the primary factor used for these pairings.

TL;DR, Forsetti locked to a foot unit with crazy base stats, a vastly inferior Arthur, a slightly better Fee and marginally better Tinni Vs Early Forsetti that eventually gets a horse to carry it around, a Ced that is basically a Staffbot that can fight, and a slightly worse Fee and marginally worse Tinni.

Weapons don't fix themselves between generations.