Bows have a long range and decent accuracy in a stage of the game where long-range firearms are rare. One gal using a bow can be really useful ratmen village maps. They have pretty low damage so gainst anything tougher than an unarmored human you're probably better off using javelins or grenades or mortars to fill the same niche.
Nope. Bows have pretty good damage early game, especially if you a gal with good stats. (It's easy to max out in a short period)
Assuming Max Stats:
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Hunting Bow, Cutting: 41 damage. Flame: 37 damage + Reliable Flame Damage (5).
Combat Bow, Cutting: 58 damage, Aqua Plastic: 60 damage & 20% Armour Pierce
Long Bow, Cutting: 75 damage
Future Bows, are a bit disappointing. This might be worth it if their energy and TU cost was reduced. You're better off with a mortar at this point of the game. It's also really difficult to get the material to build them.
Javelins have pretty good damage but terrible range and ammo count. Honestly, an archer does a better job of picking off enemies from safety while a gal with a barbarian axe or spear is more useful for taking on tanks and power armoured enemies. I also find that diverting your runts too much in the early game is detrimental for your income, so if you choose to build a large store of javelins or constantly replace them, the opportunity cost will be really high early game!
Grenades don't have the range and precision of the bow and unless you prime everything in your inventory you won't have the fire-rate either. Usually all your gals with have several grenades on them anyway so a dedicated non-launcher grenadier is a bit of a waste. That role is easily fulfilled by your riflegals.
Mortars are excellent but come much much later in the game