1 ohm coils are just fine for the 18650 Efest. You might be pushing it just a tad with the 18350's though. So I'd stick with strictly the 18650 until you get your AW IMR's.
I agree with the above.
I generally run all AW IMRs in both my regulated and mechanical mods (14500, 18350, 18490, 18650). When my daughter got herself her first mechanical mod, I decided to give some Efests from RTD a try. Three 14500 IMRs for her and two 18350 IMRs for me. I put the Efests in with my AW rotation and didn't notice any difference for about 2 - 3 weeks. Then I started noticing a gradual drop off in capacity with the Efests.
My daughter noticed it too, without me asking. She asked me why her batteries once lasted about 6 hours and now they were only lasting 3 - 4 hours. I ended up giving her my AW 14500 batteries, took her Efests, and put hers and mine away in a drawer. Pretty disappointing. Maybe a bad batch, but with two different sizes? Just my experience.