Just to followup on my original post in case anyone else is looking and comes across this.
I found and purchased two that are both high quality options, and have used them now since not long after my original post. As far as I can tell, these two options are the best available. I also have another that I purchased from the macOS App Store that I don't really like and don't use.
I do a lot of lookups everyday and having a local dictionary is much faster and more efficient than using online dictionaries.
Ultralingua (http://www.ultralingua.com):
The iOS version is available from the App Store, but the macOS version is not. I downloaded it directly from Ultralingua. The app is basically a shell and within it purchased dictionary modules are available from a few dictionary vendors, in several language. I have Ultralingua Spanish - English, Collins Pro Spanish - English, and Vox Comprehensive Spanish.
I love using this dictionary and do so every day, primarily using Utlralingua Spanish - English, but sometimes referencing the Collins dictionary. The interface is great allowing searches in either language, fast conjugation look-ups, and it has a nice feature that allows typing in a numeric number and returning the spelled out equivalent.
4/5 stars. Excellent, highly recommend. Runs perfect on Apple Silicon.
Vox (https://www.diccionarios.com):
Vox also is a shell that allows your choice of dictionary modules. Modules are various Vox dictionaries. I have Diccionario Advanced Español - Inglés, Diccionario Global de la lengua española, and Diccionario Enciclopédico.
This is a bit more pricey than Ultralingua, but the content is extensive and the formatting is excellent, making reference lookups fast. I don't like the conjugation table format and don't use it often, primarily using the extensive dictionaries. There are some native audio samples included for fair number of words.
3/5 stars. Again, recommend. It also runs great on Apple Silicon.