Nope, no weight difference to speak of.....
Bolt head.....there are different bolt head sizes for different cartridges. .473 is 308, 30-06, 6.5x284 270 etc (theres a plethora of cartridges that will run on .473.
Theres also a magnum .532 fits all the magnums except the really big mags (338 lapua, some of the larger wby mags(if my mind serves me correctly )
Theres .378 its the small. .204, .223, and those lines.
The WSM uses the .532 mag head.
Stocks, yes, there seems to be more choices for the SA than LA.

The SA will run 6.5x284 as well but the SA dont typically allow seating longer bullets out to the lands and still feed from the magazine. Thats why alot of people here use the LA even on SA cartridges. This allows them to feed from the magazine with bullets seated out as far as they want.
You can run all 3 of those in a SA. I personally prefer to use a LA for the reasons mentioned above.
Scooter