Honestly any dose of CF will interfere with your lifting in my opinion. The question I think that needs to be answered is where do CF and competitive weightlifting rank respectively on your priority list. That is, are you willing to lose some of your lifting ability in order to develop some CF style fitness? In my experience, the only people who continue to progress with the lifts while doing CF are those who have no previous experience with the lifts and therefore have an extremely entry level starting point. Seasoned lifters, however, see their progress stall or even regress as they add in CF to their training.
If you want to try to balance the two, I would suggest limiting your CF training to 2 days/week and reducing your lifting training to a lower volume, higher loading approach 3-4 days/week. Try dropping in some CF workouts after your lifting on those 2 days to give you a few genuine rest days. Unless you're from outer space or are related to Mister X, you'll find it pretty easy to do way to much work for your body to handle.