The best method is to first ensure that your mp3 tags are accurate.
The minimum subset of tags you should focus on are: Genre, Artist, and Album.
Other tags that are very helpful if accurate include: Track #, Name, and Cover Art.
Once you have good tags then you can take full advantage of MC to search, filter, and sort on any combination of the tags to find what you are looking for.
And you can then play what you have found, or put it in a playlist for future use.
If you do not have the time or energy to clean up your tags, then a reasonable approach is to create a bunch of playlists for different moods or situations and manually add appropriate tracks.
Wrt to changing a drive, it is no problem provided either you:
- copy your music to the new drive using MC, or
- copy the music to a new drive using whatever tool you want but maintain the exact same drive letter and folder structure on the new drive
In all cases you should regularly backup you MC library to protect your playlists and any other customizations you make in MC.