Supplies is a new technology that reduces the food cost of the Swordsmen line by 15 Food, making the total cost 45 Food, 20 Gold.
It is unknown how Cliffs are affected though,
The Hill Bonus stacks with the current 25% bonus that every civilization gets, so the Tatars do 50% bonus damage while on higher elevation.
I do not have the exact stats (It does slightly more attack, but it's slightly weaker than the Knight Line overall in terms of HP and Armour) or how much gold the Keshik generates per attack.
The Keshik, Tatars Unique Unit, is a Heavy Cavalry that generates gold while attacking.
The source is from EscapeAoE's recent broadcast, which featured a skirmish game on Definitive Edition between Daut and Tatoh playing as the Bulgarians and Tatars this morning.