Can you use taget scopes on stormtroopers to gain precise 2?

Yup! Keywords are cumulative.

As @nashjaee says you are correct.

I will however point out that they may be a bit overkill. I've been running Stormtroopers with DLT-19s, no extra trooper and when you roll those 6 dice (4 white, 2 red) you usually hit at least 3, sometimes 4. That leaves you with 3 misses on average which is how many re-rolls you are already getting with an Aim Token and Precise 1. If someone wants to math-hammer it out they can but playing over a dozen games with at least 4 of those squads in each game taught me that those 6 points (or multiples thereof) could be spent elsewhere.

If you're running the HH-12 and extra troopers and the like it may be more applicable but even then I won't bother with them.

Its definitely overkill. You already have 3 rerolls when you spend an aim token. 4 rerolls is excessive, especially once you've taken some losses.

Its not bad on Snowtroopers though, if you have points.

I thought it was good on snowrtroopers also. But they were going to put them on normal stormtroopers.