You can go lower depending on what regulated mod you are using. DNA30's can go to 0.5ohm builds, and there are other chips that can go even lower.
Just make sure to read the specs of whatever device/chip you are using, or whatever battery is powering your device.
I sub-ohm on my DNA30 with RDAs and RBAs all the time, but I only go as low as 0.6ohms on it just to be on the safe side. If I want to go lower I set up my mech for it.
Best of luck!
Edit: Perhaps I misunderstood your question the first read through. Clearormizers/cartomizers will work on mechs as well as regulated devices. You won't fry any tank style atty on a mech just because they are capable of putting out more power than most regulated mods, the power is held in check by the resistance on the coils. An example; I have an aerotank mega with the 1.5ohm coils in it, its filled with a juice I find pretty nasty, but it clears my pallet and brings back other flavors, I'll slap it on my mech from time to time just to clear my taste buds and enjoy other juices more. The aerotank with its 1.5ohm coils and a fresh battery putting out 4.2Volts will only draw at absolute most 11.76 Watts @ 2.8 amps. The same mech, with the same fresh battery and an RBA/RDA set up with say a 0.5ohm coil build will be drawing 35.28 Watts @ 8.4 amps. It all depends on the build, in things like protanks and the like that is predetermined by the coilpack.
Here is a link to an Ohms Law Calculator I use all the time, its good to have around when tinkering and checking safety margins.
Ohm's Law Calculator