Hello Katy,
I'll try to respond the best I can.
1. Tax Parcels are parcels that have been identified for the purpose of sending a Tax bill for a specific unit of land. In your example, it sounds like the assessment information (situs address, owner name) has been tethered to the unit of land, but these could still be considered tax parcels. The major difference that you should be concerned about is legal-lot parcel vs. tax parcel, many times 2 or more lots (or portion of the original lots) are reconfigured to create tax parcels. Imagine a legal description of "A portion of land being described as Lot 1 and 2 of Green Acres Subdivision", or the "East 15 ft. of Lot 1 combined with Lot 2 of Green Acres Subdivision".
The screenshot below is a good example. The dashed-lines represent the originally conveyed lots vs. the solid lines representing the taxable unit of land.
[ATTACH=CONFIG]30121[/ATTACH]
2. Condos can be modeled and edited in such a way that you enter each Unit (Lot), Tax Parcel, Limited and General Common Element, etc. as individual geometries. To accomplish this, use the Lots and Units Parcel types as part of the Local Government Information Model.
[ATTACH=CONFIG]30122[/ATTACH]
3. Managing the PLSS as part of your parcel maintenance workflow can be an important decision. Before doing this, we recommend that you "vertically" align parcel types that should share a common boundary before loading them to your parcel fabric (this goes for any parcel type and not limited to PLSS)
If you don't choose to include the PLSS into your Parcel Fabric, you will most likely still need it to create new parcels as they are recorded. As an example, if new description references a section corner, 1/4 corner, etc. you'll need to "snap" the origin connection lines to this point in order to find the POB (point of beginning). In this example, if the section corner is not aligned, or non-existent, it will make your job difficult. For this reason, many local jurisdictions maintain their own version of the PLSS that align with their Parcel Fabric (that may or not be more spatially accurate).