I design instrument approach procedures and can assure you that a certain amount is allowed for "sink thru" in calculating the DA/DH. The concept of being prepared to go around at DA/DH is based on the assumptions made in the design of the procedure. It will vary for different categories, but isn't a good idea for you to bust the DA/DH in the hope of seeing something!
Yeah, yeah... I know...
As for the altitude actually used by different aircraft types, it all depends on what, if any PEC is required. For example, I know that in my B200, PEC is zero, so I don't need to make any adjustments. Likewise for any aircraft types where PEC might be a negative value.