Shoot for around 2900-3000 weapon damage, at least, without the temporary buffs like Alchemist. Like Mauz I run Marksman/Alchemist (my second bar is DW, not 2H). I run with Agility jewelry instead of Leki's, which I can do because my 5-piece alchemist set includes two weapons.
For crit I just take whatever those sets get me. As a Khajit in medium armor with a bow, I'm over 40% crit. No need to boost past that.
As for penetration, I have that as my weapon trait (sharpened) and I boost it via champion points (Piercing). Can never have too much armor penetration in my book. There aren't that many sources of armor penetration when using a bow, really: weapon trait, champion points, and a couple of weapon sets that you won't use. DW, 2H and Destro Staff all have passives that apply only to those lines.