I'm no historian but I am a lawyer.

From my experience, most constitutional law from the 1780s-1800s involved simply defining/interpreting the fundamental Articles of the Constitution, not the first ten Amendments to it.

Cases like Marbury v. Madison, a fixture of constitutional law courses in school, where SCOTUS basically helps define exactly what the powers/roles/limitations of the three branches are because nobody knew exactly how government should function in 1803. The duties and responsibilities of government are innumerable but the text of the Constitution is extremely sparse. So a lot of "interpretation" had to be done to figure out exactly how each branch would function, where their jurisdiction ended and another branch's began, what powers the federal government would have over the states, etc.

I think the famous quote "this is a Constitution we are expounding" is in Marbury. This was the Chief Justice emphasizing how important the case was, along with the current mission of the government, for delineating the function and establishing the permanence of the highest law in the land going forward.

To a certain extent, yes.

Barron v. Baltimore(1840) stated that Bill of Rights did not apply to the states. Moreover, the majority of judicial proceedings are performed on the state level, so anything that determines state law will necessarily affect the majority of judicial proceedings. Where the concept of the Bill of Rights applying to the states begins however is with the inclusion of the fourteenth amendment in 1868. The relevant text in the amendment is the section stating that "No State shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any State deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws." What the Supreme Court would eventually decide as a result of this amendment was that the Bill of right by and large did apply to the states. However, these decisions did not start being made until the 20th Century, and most of them were made during the 1960s in what was known as the "due process revolution." Up until that point in time the Court left it up to the individual states to interpret them and decide what exactly the Bill of Rights meant. As a result, most of the power in judicial proceedings before then was left in state law and in the specific legal processes of each state.

To get some historical context, an important case to examine is Hurtado v. California(1884). This is the case where the Supreme Court sets forth that the states have latitude to decide what the bill of rights meant in the context of their state. In this specific case, it meant that although the fourteenth guaranteed due process California could decide that the right to due process did not include the right to a jury trial-in a capital case no less! As I have stated before, the only reason there was even any question about California's ability to do this was the fourteenth amendment. Without the specific section that targeted due process, there would never have even been a question about whether California had the ability to do this.

Where the court really begins to change the view it established in Hurtado is in 1932 with the case of Powell v. Alabama. What the Supreme Court dictates here is that the state so egregiously violated the rights of the defendants with regard to their right to a lawyer that they were denied the due process. Here the Supreme Court begins its practice of dictating to the states exactly what the rules are with regards to specific aspects of the judicial process.

Backpedaling a bit-at the turn of the 19th century, the Supreme Court does start enforcing some of the provisions of the Bill of Rights, specifically those directed at search and seizure, but only towards federal officers. This results in what is called the "silver platter doctrine." Federal agents were bound by the fourth amendment. If they violated the fourth in their investigation any evidence they seized as a result of that would be suppressed in court. This is known as the "exclusionary rule." State officers were by and large not bound by this rule. As a result, federal officers would tip off state officers who would then perform warrant-less searches. The evidence they seized could then be used by the federal agents in court.

The next two cases, Wolf v. Colorado(1949) and Mapp v. Ohio(1961), are closely tied together and deal with the aforementioned "exclusionary rule". In Wolf, the Supreme Court ruled that the fourth amendment was enforceable against the states, but left it up to the states to decide the remedy for warrant-less searches and seizures. By 1961, a number of states had not done so, so the Supreme Court ruled in Mapp that the exclusionary rule was enforceable against the states.

Mapp v. Ohio set the stage for the "due process revolution" of the 1960s I spoke about, where the Warren Court ruled in a number of cases in favor of due process over the end result of criminal proceedings. This process formed the basis for many of the rights that we enjoy today. If you're interested in specifics Brady v. Maryland, Miranda v. Arizona, Escobedo v. Illinois, Gideon v. Wainwright, Katz v. United States, and Terry v. Ohio were all important cases in this process. Terry v. Ohio is especially interesting as it forms the basis for all stop-and-frisk searches today.

Source: Criminal Procedures 8th ed., Joel Samaha

There are a couple of reasons for this. First, bill of rights was a limitation on the power of the federal government, not the states. Second, there were not many federal laws that impacted people on an individual level. Most "everyday" legislation was left to the states. Third, early constitutional cases tended to involve issues of balancing power between the three branches of government. Fourth, prior to the civil war there was a strong belief that individual states could nullify federal laws they did not agree with and even that individual government officials were duty bound to not enforce laws that they believed to be unconstitutional. Even after Marbury vs Madison, it took a while for society to recognize the judiciary as the final arbiters of whether a law was constitutional.