Are there any advantages to using the All Stars + World ROM? Can you use the mechanics of the first 4 games, in SMW if you use that ROM? I know probably not, I'm just wondering.
A weird question about SMAS
No, they don't, since all the 4 games in that ROM take up enough space as it is. No mechanics can be imported into Super Mario World piece of the ROM. You need an entirely clean SMW ROM (not SMAS) if you want to implement mechanics such as sprites and graphics, that way, more space can be used.