Talking about the last first this is a couple of innovative sets called 'Hell and ' - so for example Hell and Fateful Decisions. These are out of print and difficult to get but very interesting. They need a bit of work to use but something I keep meaning to have a good go at.
So I haven't played the Hell stuff much but we have played a lot of Spearhead. It is relatively large scale so a player will command a large-ish real formation - typically 5 or so battalions, a reinforced brigade/regiment. The system is simple and easy to pick up with a nice way of reflecting national differences.
2: 1 1/4" square bases with 1 vehicle or 5 or so figures on - but you can put what you like.
3: We haven't played this scale much recently so I am not sure what everyone has. Andrew W (Dan's brother) was/is doing this and he has all the troops I know about. These are loads of British and Italians for circa 1941 in the Desert. Also an entire US (OK actually Free French but they are the same) Armoured Division and a British Infantry Brigade for circa 1944 Italy/France. We have also talked about doing Russia but haven't actually done it.
As you will see we are short of Germans as the guy who had these moved away. This means we have only done the Desert recently.
I have been playing quite a bit of 6mm WWII over the last 12 months or so having found a new set of rules (Combat HQ). I chose these rules as they seemed to have all the elements that the other rules we were using at the time were missing and were having to write in house rules for. Since Finding the rules I have been working with the Author to further improve them and take them forward.
The Game is designed to be fought at Battalion level with attachments with the basic unit being a Platoon of infantry or a squadron of tanks. I have been basing my figures on 50mm by 30mm Bases, as I feal this fits wit the ground scale and looks effective.
I am happy to run a game if you are interested. I currently have British and German forces for 1940 and Russian and German forces for 1943 so can do either. I am away this weekend so a game at the club would have to wait for the new year.