From experience on someone who ran a lot of spy 2.0 since it came out,
Thermite round, Scorch, Frigid Blast, Frostbite are drop at Pluto which I believe to be a T3 reward for spy 2.0
Rime Round at Sedna Scylla which should be T2 reward. (There are 3 spy mission in Sedna, not sure if they all yield T2 reward)
Volcanic Edge and Vicious Frost are drop at Jupiter T1 reward.
I have gotten these mods from running these mission so it is comfirmed that they drop in these places. Rumor has it that scattering inferno drops at T2 reward which should also drop in Sedna Scylla. If anyone have gotten one from T2 reward please let us know.
Also, if you're not sure which tier that area is, you can check the other 2 reward mods.
Generally they are similiar to the Survival rotation A mod drops.
If it's power throw, stablizer, steady hand, it should be T3.
Point strike, blunderness (primary, secondary common/uncommon mod) it's T2
If it's melee mods like parry, reflection, it should be T1.
These are my observation from running spy 2.0, free feel to correct anything that is wrong.
oh and for some weird reason T2 reward gives T4 sabotage, while T3 rewards give T3 and T2 keys.. odd