I guess the standard way to do this sort of thing these days is with a bandsaw. And keeping the first waste piece cut from each piece can prove very helpful with this method so that you can tape it back into position to provide support for the piece when you cut the second curve.
As long as the wood isn't too hard or the legs too big I think you could do much the same using a scroll saw, even though they are not ideally suited to cuts of this kind.
Not that I'd recommend it but the entire shaping job could be done using a belt sander, starting with a very coarse grit (i.e. nothing finer than 60).
In theory the same basic method as used with the bandsaw could be used with any curve-cutting hand saw (e.g. jigsaw or bow saw) as long as you can work out a suitable way to hold the workpieces for cutting, using one or more clamps or a vice.
But because these are relatively small and not complex like a cabriole leg I'd be tempted to do this type and amount of shaping without recourse to a saw. There are a few options here:
Use a 2"/50mm chisel to hog off the bulk of the wood that needs to be removed and then refine using a spokeshave.
Do all the work with a spokeshave. Relatively slow but definitely doable if needed.
Scrub/roughing plane to waste the majority of the wood and then switch to a smoothing plane or block plane to complete the shaping. With a bit of practice this is a surprisingly fast method (only minutes per side) and if you do the smooth-planing well no further work would be needed on the curved surfaces and the legs would be ready for finishing.
Use one or more rasps to remove the bulk of the wood, then switch to files to smooth. I wouldn't recommend this method as it would be the most labour intensive and slowest, but it is possible to do it this way if other tools aren't available. Make sure you've had your Wheaties that morning if you go this route!
Regardless of the shaping method chosen as much final smoothing as is needed could be done with some combination of file work, scraping and sanding (sand using a firm block to protect against accidentally rounding corners).
Obviously a stationary belt sander could be used for this as well if you have one.
Templates for consistency
In all cases a cut out template in stout card or hardboard would be a very good idea. For the bandsaw method this becomes your master template to draw the required shape on each facet of every leg, and for the hand-tool methods it can be held against the legs during shaping to check progress.