Sarmatian BGs have 6 Bow Attack, and a 5-Attack, .4 Lethality, AP Spear with a 44 Charge value. They have 22 Armour and 12 Defense Skill.
The Early Parthian BG is the exact same, except they only have 20 Armour.
The Saka BGs aren't quite as bad - they've got the same Spear/Lance as the other two, but their other weapon is a .165 Lethality AP Axe with 10 Attack, and they only have 18 Armour.
Parthian Cataphracts have the same Attack stats as the Saka BG, and have 20 Armour and 10 Defense Skill.
Hellenic Cataphracts have a Sword for their sidearm (10 Attack, .11 Lethality, AP), 22 Armour and 8 Skill.
Now, for the Noble units:
Parthian Medium Nobles: 5 Attack Bow, 4 Attack Spear with 34 Charge. They have 9 Armour and 9 Skill. They are available in over 20 regions.
Dahae Noble Cavalry: 6 Attack Bow, 4 Attack Spear with 37 Charge. 14 Armour and 9 Skill. Five regions.
Sarmatian Nobles: 5 Attack Bow, 4 Attack Spear with 33 Charge (.33 Lethality). 10 Armour, 11 Skill. If I understand the map correctly, the Sarmatians can recruit them - literally - in every province (other factions can recruit them, but in limited areas).
Roxolani Nobles: 6 Attack Bow, 5 Attack Spear, 44 Charge (back to .4 Lethality). 12 Armour, 12 Skill. Similar Recruitment area as Sarmatian Noble HAs.
Saka Armoured Nobles: 6 Bow, 4 Spear (44 Charge); 19 Armour and 10 Skill. Map is broken, so I can't figure out where they're found. There appears to be a Bodyguard version of this as well, with a 5 Spear and 18 Armour.
Early Saka Nobles: 6 Bow, 4 Spear (33 Charge, .33 Lethality). 10 Armour, 11 Skill. Available everywhere.