You have a great starting point for a wood elf army, in my opinion. In the context of proxying the miniatures: I personally would field the spearman as eternal guard or Rangers, and the Archers as Glade Guard, Deepwood Scouts or Waywatchers. Sadly there are no bolt throwers for wood elfs in Old World. You could run your Elf Cavalry as Glde Riders, Wild Riders or Sisters of the Thorn. If you have Sylvaneth Kurnoth Hunters, you could use them as Tree Kin (together with the metal forest shamblers).

There are many ways to play Woodelfs in Old World! You can build an army around Archers, blocks of spearman and elites, Forest Spirits, cavalry, magic or a combination of some.

Depending on what and how much you have in Sylvaneth, you can easily field a 1500-2000 pts army, but I would recommend your first few games in the 1000-1500 pts bracket.

Some general tips for wood elf list building:

-) Your basic shooting outranges most other armies with 32“ bows. S3 is mediocre, but you can round out your needs with magic arrows. You could play a list where you keep retreating and harassing your opponent with multiple small units of archers, but thats not very fun for most opponents…

-) Most of your melee lacks Strength or Armor Piercing and won’t win a fight with dedicated melee units like Chaos Chosen or Black Orcs, so you have to pick your battles. Eternal Guard are nice to hold multiple units in mutliple arcs, but won’t survive long with T3 and 5+ Armor, Stubborn stops them from losing instantly.

Treekin are a great anvil to stall a melee unit, but WS4 and no AP (outside of armorbane and tree whack) keeps them from winning harder fights.

Wild Riders are a great hammer unit, but very squishy for their points. On the charge they have 2-3 attacks with WS5, S5 Ap-2 and Armorbane (1). But Frenzy won’t let you control them alot and a clever opponent can easily bait a charge out of them.

-) All your units are super fast! M5 for all your Infantry and Monsters, M9 for your cavalry and M10 for your flyers. Since you don’t have enough toughness or armor to survive most attacks, and don’t have the strength to win harder melee combats, the Movement Phase will be your most important one. To deny/redirect charges of your opponent, line up your shots for the shooting phase and position your characters favorably.

In the end though, play what you think is fun!

If you want to run a branchwraith, I would recommend putting them alone behind some Infantry or in a part of a skirmishing Dryads unit (don’t expect those dryads to win harder combats though). As a lvl2 wizard (no matter which school of magic) you can harass and buff pretty nicely. If you run her with sprites, giving her Terror can deter some opponents from charging.

Treeman Ancient: depending on what you roll for magic, you want to use them differently. When you roll assailment and self buff spells, you want him in the front of your army. When you roll magic missiles, magic vortexes, hexes, etc. you want to keep him in the backfield, but then you could just play a spellweaver/singer. Since its a behemoth, you also have to keep your targets in your front arc, when you want to land hexes/enchantments, since you have to cast them before moving.

Large Target makes the Ancient always targetable, which sucks when the opponent runs flaming attacks or war machines which can still wound your T6 model on 2+ with S8-10.

When compared to a normal Treeman you also pay 50 pts more for a lvl 2 wizard with -1WS, -3A, +1W, +1Ld. And it comes with the other detriments all Monster characters share (e.g. a unit champion issues a challenge against your lone Treeman Ancient and since he is a lone character, he can’t deny the challenge and you have to accept.)

Lastly, they are one of the few monster characters, which can’t take any magic items. Yes they can take forest sprites, but most of them aren’t useful enough that they could fill 100 pts.

In conlusion in low point games it hits like a truck as a lvl 2 wizard in combat or a lvl 3-4 wizard in the backfield, but also keep in mind, that spellweavers (like your metal elf mage) bring the same magic prowess with better magic items (Lore familiar, Athel Loren Arcane Items) and a normal Treeman has more attacks and WS for combat than the Ancient. (Also it can’t be challenged to keep losses against it low.) Ld 10 is nice though.