As you'll see in the Coberage, it gives on-line access to more recent data than familysearch; but to avoid wholesale identity theft, effectively places a 100 year embargo.
However, a personal visit to Register House in Edinburgh gives access to much more recent data, up to about two years back (process limitation of gathering the data centrally etc).
Frequently an SKS visiting RH will look something up for you; or you can employ a professional genealogist in Edinburgh.
RH itself will not carry out genealogical searches, that is not its function.
If you can supply sufficient details of, say, a person's birth such as Name, Date, LOcation etc, they will look for the nearest match; but will not pursue vague requests.
Scottish BMD certificates will normally have a wealth of other information such parents' names, occupations, locations etc, depending upon what the Informant supplied (and as accurate/inaccurate as that person's knowledge covered).
Keep in mind that for the OPRs (Old Parochial Records) prior to the 1855 SR (Statutory Registration) have been subject to two or more centuries of turmoil, time, water, flood, pestilence, vermin, war etc, so they are far from "complete".
The Wills on SP cover about 5% of the population as 95% did not leave Wills or much property etc to be dealt with.
However, it is always worth trying the Free Index Search of the Wills, as the Description column can frequently have useful details.
Scotland is fortunate in having many on-line sources of data, so using a general Search Engine may pay dividends.
Two of the three "Statistical Accounts of Scotland" (about 1770 and 1840) are available as well, written usually by the local minister of the time. These give good descriptions of the general conditions in each of the parishes; and occasionally you may find mention of an ancestor or details of the place lived in.
The Mitchell Public Library in Glasgow has the biggest Reference Department in Europe, with local Trades Directories etc. It may also be able to give you the addresses of local family history groups, the latter usually having good contacts with the public library system over here-