These are not load bearing walls, so anyway that will work is OK. A method of anchoring to concrete that I have found fairly easy is to use a hammer/drill, lead ferrells, and screws. What I do is to cut the 2x4 to size abd drill holes in the where I want to put the screws. Then hold the board in place and drill into the concrete using the board as a template. You can do one, then put the ferrell in, screw the board to the wall, position it for square, and drill the rest of the holes. Then swing the board aside to access the new holes. I also use screws for most of the carpentery work when doing this kind of job. Sure makes it easier working in places where you can't swing a hammer not to mention being able to easily remove and reposition if you get something out of place. I invested in an inexpensive rotary/hammer drill for these kind of jobs. Sure is a handy tool even if it isn't one I use everyday. (Something like $100 including a few bits and chisels)