The most efficient CFL are the 23-26 watters. 100w equivalent.
If your going with just 2 autos, id do 4 or 5 bulbs a piece.
I had a few plants under 23 cfl bulbs and 2 4 foot T-8's. It ended up costing more and was alot harder to get rid of the excess heat than the 600Whid i have now. My first 2 grows were with cfl. its MUCH hardert to get the yield, you HAVE to keep the plants short. LST them. Top them if theyre not autos. Keep the lights close (but not tooo close) 1 or 2 inches people will say is good, but trust me even though they dont burn, keep the lights 3-6 inches away and you will see increased growth.
I had excellent results with CFL and theres nothing wrong with them, dont listen to people that say u cant grow good weed with CFL. You definitely can, its alot more work and will cost more money IMO. Id go with a 250-400w HID for some autos instead. Check ebay theyre cheap nowadays. Bigger yield less work. The new ballasts even take both MH and HPS bulbs and you can switch em from 150,250,400 w, or 250/400/600, or 400/600/1000 depending on which one.
Peace and good luck
check out my 14 strain grow
https://www.rollitup.org/indoor-growing/748887-multi-strain-grow-600w-15-a.html