Please note that the Big-Y test has supplanted custom SNPS. If you want to compare with others, Big-Y, because all inclusive that scans all your SNPS, is the way to go (3/8/2023)
The Smith DNA project is a surname project where, primarily, YDNA STR results are compared by haplogroup to find matches. Members can look at FamilyTreeDNA matches by logging on to FTDNA; FTDNA shows which testers from within the entire database of testers, regardless of surname, a member has a match with. Depending on how many markers match versus how many do not, a person is deemed to be related to someone else on a range of very tightly related to not related.
What about SNPs? The first question to ask yourself is what information you are hoping to learn from getting additional SNPs. Generally, the Smith DNA project believes there are 2 reasons, within our own project, that you would want to get additional SNPs. The first is that you want to examine your deep ancestry, going back hundreds or thousands of years to compare origins with others that have the same SNPs. The second is that you match into a grouping and you and the others (or another) have decided to jointly get a particular SNP done to see if you continue to match.
Researchers are able to identify these SNPs genetically but many of the SNPs have not been associated with ancestral population or geographic origin. This means there is a goal to find more recent ancestral migrations associated with newer SNP, but we may not know a whole lot more than what we currently already do once the results come in. The Smith DNA Project suggests that you join a Y-DNA haplogroup project (which typically deals with deep ancestry versus surnames) to get further assistance with SNPs. The volunteer admins on a Y-DNA haplogroup project are often able to suggest specific SNPs based on how you match others, regardless of surname, within the database. This can be helpful for targeting specific SNPs that you could be positive for rather than randomly testing a whole bunch at one time. Here is a list from ISOGG of the Y-DNA Haplogroup Projects. We suggest you click the link to the haplogroup project, read about the project and then contact the project administrators for more information, including how to join.