My next question is this? Will there still be the same continuations as before...in other words, will the ABCZ glossaries still make full use of all the features offered in IT?The commercial ABCZ glossaries make full use of all the features offered in IT. The continuations, for example, work fine alongside glossaries from TAMED2 and Judy's Drug lists, which I use to do my transcription work. If you build your own ABCZ-style glossaries, they too should work well with all the features of IT. You do need to set them up well so that things mesh. E.g. as above, put most words and two-word phrases in the Phrases advisory. You can also have a giant wordlist in the Words Advisory as a supplement. (TAMED offers such a glossary.) Also the order of your glossaries in Includes matters.
....are the shortcuts for the continuations converted to the ABCZ method also? When you do a
multiple compilation, you do not need to worry about converting Continuations to ABCZ format. If there is a short from for the Continuation, it will be the first letter of each word in the continuation and this is supplied automatically. (This is the same as the ABCZ format when the phrase consists of 3 or more words. The ABCZ rule is aaa...first letter of each word.) (Of note, some Continuations appear without any short form. Perhaps Marianne will explain the subtleties of this.

I haven't worked with
Enrich much and perhaps too Marianne will offer a comment on any particulars one should be aware of in using Enrich and then converting to specific rules like ABCZ or blending the enriched entries well with Continuations.
With some tweaking, IT might well become more productive for you than Shorthand. As I've mentioned before, though, almost exactly half ABCZ customers order the glossaries for Instant Text and half order the ABCZ "dictionaries" for Shorthand/Speedtype. I think this is based on preference for the features and perhaps cost of one expander or the other, and not on how well ABCZ integrates with either expander since ABCZ methods work well with both. One key to success with either expander of course is the fine visual advisories which both offer. (For anyone using an expander without visual advisories - they can make all the difference in applying one's shortcut methods or system of short forms.)
Jon