You can add almost as may action to an action group as you like.
Also, you can create a set of action groups if you tick their entries in the Actions ... dialogue. They will be executed top to bottom (so it may be necessary to move one or to to get the right order).
See this thread on the Grammartron case conversion:
Either use Convert>Tag-Filename or an action of the type "Format value" for _FILENAME
Format string: $num(%track%,2) - %title% (%artist%)
I do not see much hope here to do that with an action as each action only looks at the current file and does no know anything about previous or coming files.
There is the Track Numbering Assistant, though, but that relies on folders to detect that now a different album or CD starts. So unless you have arranged your files by indiviudal folder already, you have to either have to create such a structure or select the files group-wise.
This split may not be necessary for case conversion, copying data to comment and for new file names.