Almost all judges are weaker or stronger at some kinds of cases. Most judges have backgrounds either in criminal law, or in personal injury law, or as government litigators, although there are exceptions to the rule. Lawyers with a background primarily in non-criminal legal specialties, in contrast, are usually weaker in the area of criminal law. And, lawyers with a practice general enough to have equal aptitude in all commonly litigated areas of law are usually not prestigious and well connected enough to be appointed to, or elected to, judgeships as the case may be.
Even within specialized judgeships, like designated probate judges, some are stronger in protective proceedings, like guardianships, and others are stronger in areas like technical tax oriented trust interpretation and technical probate rules governing the interpretation of wills.
Do court systems track the above in any way and tend to assign judges
cases in areas of law where they are strong, and not where they are
weak or is it "potluck" whether a client gets a "1" level judge or a
"9" level judge in the law relating to their particular case?
Courts do not track this and for the most part it is "potluck", but some courts have unofficial internal administrative divisions such that, for example, certain judges handle domestic relations cases for a while, while other judges handle criminal cases for a while, and other judges handle ordinary civil cases for a while. Usually, these assignments are rotated from time to time, but these informal internal divisions sometimes reflect the preferences or expertise of the judges.
Similarly, on the U.S. Supreme Court, while each justice has an equal vote, Justice Gorsuch, with a background in Indian Law, is more likely to be the author of a majority opinion on Indian law, that Justice Alito, who has no background prior to his U.S. Supreme Court appointment, in that area of law.
The law does not take judicial notice of this fact. Indeed, it does the opposite. It conclusively presumes that judges are experts on everything that comes before them, whether this presumption is well founded or not. On questions of law, it doesn't matter, because those questions are reviewed de novo on appeal without any deference to how the issue was resolved in the trial court. But on issues of discretionary determinations, findings of fact, and evidentiary issues, judges are afforded broad discretion and deference, whether or not this deference is well earned in light of their personal experience.
Indeed, one of the more common sources of bad judicial determinations which are upheld on appeal is a standard of appellate review for a decision that affords a judge who has no clue in a particular kind of transaction or area of law great deference.
For example, I once had a case before a judge with a background as a violent crimes prosecutor who was stunned to learn that stockholders of publicly held companies are owners of the company, and thought that one could determine the fair market value of a company several years in the past, by calling up its accountant without warning and having a five or ten minute conversation with the accountant. A factual determination based upon that approach, as disconnected from reality as it is, would receive great deference on appeal, despite the judge's obvious unfamiliarity with the basics of corporate law and business valuation.