WAB and COE match up. Even HC can use WAB/COE basing with a movement tray since the unit is the basic block of miniatures. COE and WAB have miniature removal for losses and generally use a movement tray fitting to the current formation.
20mm x 20mm for infantry in COE/WAB. Skirmisher types can be based on a wider 25mm x 25mm basing but not required. Cavalry on 25 x50mm basing,
EL and Chariots etc on larger bases.
HC is based by the unit
.could be a single block of miniatures on one base.
but generally most ancient gamers tend to the COE/WAB basing for HC so they can interchange between all the rule sets.
Played 28mm COE and WAB. HC is a pending project. HC "seems" to have a following for 15mm since the armies, miniature count wise, tend to be larger than COE/WAB collections
.but not a requirement. My ancients gaming group has thousands of 25mm/28mm miniatures
.so common basing format between all three game/rule sets is a priority.
Look at some of the AAR posted on this TMP site and other ancient gaming sites or blog pages. there are many examples and creative ideas for basing.
Sorry, no info about W&C
.never played or seen a game in california.
Tall ears from the warren. WR