Underbarrel laser sights can be attached to bows. Maximum mods on a bow are something like underbarrel laser sight, bow stabilizer or bow stabilizer system, single pin sight or 5 pin sight or bow scope, bow dampening kit, and arrow rest. Almost all of them are craftable with Fabrication 5+, Archery 5+, Electronics 5+, and a copy of the Bowyer’s Buddy.
Wooden Greatbow has dispersion 200, reload 100, range 12, damage 35, weight 3.2 kg. The compound Greatbow has dispersion 100, reload 150, range 22, damage 60, weight 2 kg. You’re almost certainly better off using the compound greatbow.
As far as achieving 18 ST:
Start at ST 10.
Install a Muscle Augmentation CBM for ST 12.
Drink some Ursine, Cattle, or Lizard mutagen for the Large mutation and ST 14.
Inject a lot of Chimera, Lupine, or Troglobite serum for the Extremely Strong mutation at ST 18.
Alternately:
Start at ST 8.
Inject a lot of Ursine serum for the Huge mutation and ST 12.
Inject a lot of Ursine serum for the Insanely Strong mutation at ST 19.
Bonus: You’ll probably pick up TAAANK on the way, for +40% HP, and Shaggy Fur, which will keep you warm now that you can barely wear clothes and don’t fit in vehicles.