Just to give a bit of background regarding your question in point (2)...
SQL Developer is a Java application and, as such, really has no 32-bit or 64-bit version. It all depends on whether SetJavaHome points to a 32-bit or a 64-bit JDK. Prior to 4.x.x, the SetJavaHome may be found in the sqldeveloper.conf in the install directory. For 4.x.x & up, look instead in the product.conf file under the user settings directory (%APPDATA%\sqldeveloper\<version>\product.conf). For 4.x.x & up, the sqldeveloper.exe is smart enough to know which it is calling.
SQL Developer, prior to the 4.x.x release, strictly as a convenience, provided a download zip for Windows that included a 32-bit JDK. With the 4.x.x & up releases, this changed to a 64-bit JDK. Why? Due to the increasing prevalence of 64-bit OS, in general, and because Windows continues to be the most popular platform. So if you were to compare the contents of sqldeveloper-18.104.22.168.59-x64.zip with sqldeveloper-22.214.171.124.59-no-jre.zip, the only difference you should see is the inclusion of a sqldeveloper\jdk folder in the x64 download.
And if you do use the x64 download but wish to install and use a more recent JDK than the 1.8.0_45 it contains, just update product.conf as needed.