Okay. So, I have the impression you have limited building experience. So what I would recommend is a Topside (which will give you enough power for any single coil bf rda in the future) and then head to vapinart.com and do a search for nocode. The nocode tired and nocode lazy are compatible with bvc and ego one coils respectively. They also have small chambers and give very decent flavor.
If, however, you are an experienced builder then it would depend on single or dual coil setups as your preference. Almost all atomizers released in the past year are bf compatible. Budget plays a role in your choices for single coil rdas but for dual your options will be what you already know.