I have seen the Greek figures and indeed they are not their best ones (however they provide infantry support weapons). EWM started many years ago as "Tom's Tins". Some figures / kits date from those days, with Tom Lobley still adding - usually excellent - figures. His range is distributed by EWM now, as is the former Skytrex range, plus figures and kits form other sculptors. That's why the range includes different quality levels.
Size-wise, I found some figures go perfectly well with 22mm Airfix, and I believe they were produced back then to add variety to those. Other EWM figures like the WW2 Indians are a perfect match to HäT's 23,5mm WW1 Indians.