precisely
you don't need anything holding them in place, screws etc., as the camber block hingepin (that goes through them) holds them in place.
personally, I change from one variety to the other primarily dependant on the track/layout. for tight layouts I use in-line axles (for quicker steering response), and for highspeed tracks with more wide open corners I use the non-inline style. but it's a personal preference thing.