I'm vaping a Nemesis and Trident clone right now. I've not tried the Astro, but it gets great reviews on FT. If that is what you want, I say go for it.
The Trident will make a lot of vapor if you set it up that way. It comes with one dual air holes option which are not big - I estimate under 2 millimeters. It also has three single air holes which I think are even smaller then the doubles. You definitily need the dual joles for dual coils. If you go below about 0.6 ohms combined dual coils in it I would suggest you should think seriously about drilling the air holes bigger or you will be pulling really hard and wasting the battery power for no gain. Check out
this video for more info on it.
Your battery selection and a good charger will be critical to safety for low ohms. Hopefully your friend understands this, but not everyone who does this knows. You can read about batteries for low ohm use
in this thread. Basically, the lower you go in ohms the more amps (power) you draw from your batts. If you use too much for too long the battery will start to heat up. Get one hot enough and it will vent gas, which is nasty stuff and venting can get dangerous as well.
Vape safe