What's the Steel Club weight equivalent to a set of 16kg, 24kg, and 32kg KBs? Assume reasonably fit male.
I don't think there's a very close equivalence, both because the implements and drills are different in nature, and because clubs vary a lot in feel based on length and weight distribution (longer = harder/more weight toward the head = harder). I definitely prefer a longer club with more weight toward the head for a better, "swingier" feel, as well as being more challenging for a given weight.
For instance, the Rmax/Tacfit clubbells and Oates TAP Bell Clubs are much longer (in the range of 26-29" depending on weight) than the typical generic Chinese clubs sold by Onnit and many others. The CK Maceworks plate loadable Cadi club is 24" plus the length of the plate stack, which is long enough, plus the weight distribution is more toward the head. The Adex regular club handle is very short by itself, and weights are barrel-shaped so the length of the club varies a lot depending on how much weight you load it with. People make spacers out of PVC pipe to extend the length and keep it consistent when using lighter weights. Adex also has the ARC handle, which is 26" long. That might make is hard to do circles and mills without hitting the floor if you add a lot of the Adex weights, which add a lot of length. However, it is possible to kludge regular 1" plates onto Adex handles, and 3/4" PVC pipe makes a nice spacer sleeve to keep the plates from rattling, although you need to cut separate sleeve for each combination of plates to make sure the length of the sleeve matches the height of the plate stack.
Because of the leverage and momentum of clubs, small differences in weight make a much bigger difference in feel and difficulty than with KBs, and there is a much bigger difference between one and two-handed drills.
All that being said, in the context of the Rmax/Tacfit clubbells, with which I have the most experience, I'd recommend 15lbs as a good beginner weight for 1-arm drills for an average fit male (someone comfortable swinging, pressing and snatching a 24kg KB) and 25lbs as a beginner weight for 2-arm drills. However, as an equivalence to a main working weight, I'd say that a 15lb club is closer to a 16 or 20kg KB and a 25lb club is closer to a 28 or 32kg KB. A 20lb club would be somewhere in the middle.
The new generation Tacfit clubbells and the Oates bell clubs come in kilos, so instead of 15lbs, Tacfit has a 7kg and Oates has a 7.5kg, and instead of 20lbs, Tacfit has a 10kg and 12kg, and Oates has a 10kg and 12.5kg. They also come heavier than that, but most people will have to train a long time to use heavier clubs 1-handed, and longer than that to build any kind of volume. I've been using clubs for decades, although not continuously, and the heaviest clubs I use for 1-arm overhead drills are 12kg. For 2-arm drills I go up to 45lbs.
The loadable clubs (the leading brands are Adex and CK Maceworks) are flexible in terms of load, but more expensive, and similar to adjustable KBs, VERY annoying (at least IMO) to change weights on the fly in the middle of a session.