Rapid-rooters are a good medium to clone- they are made of composted bark.

For strains that are not cloneable, any autoflower strain is pointless.

I had some trouble getting strawberry cough to strike in the past.

I find that the hardier the strain, the easier to clone. So look at Afghans, NL and NL derivatives, anything derived from Thunderfuck, Skunk #1, etc.

Your technique will play a large role, prepping mothers properly... you already know about buffering effect; good. Mothers need to be deprived of N for a week or so before taking cuts, and be very healthy otherwise... I have found that Ca and K deficiencies will drive your % survival to or near 0. So will N overdose.