pauljbrennan, they're very similar.
Both fire on the CLOSED bolt, both have the mauser-type rear sight and tunnel-type front sight with extra inserts. Both have the inserts in a capped storage well in the butt of the their pistol grips.
The A7 was their "flagship" and cost a few bucks more than the A3, plus it had a couple more sight inserts. Plus it had more checkering, etc..
Here's a pic of my A7, as compared to my A3 in the previous post.
ONLY the E1 takedown carbine would accomodate the 20-rd magazine, while the other 3 North American models for import used ONLY the 8-rd mag.
I have no experience with ANY of the aftermarket magazines. My guns all have original Gevarm mags. Sorry I can't advise you on those.
Best regards ~ ~ ~ FFF