Would someone please provide a brief description of the various models . . . Regency, Breakaway, etc. Thank you

There are a variety of models - as you probably already know. A good place to start as a primer is the Barths for Sale forum and check out the first five threads.

More info (mostly photos) is on the Barth CD, which can be ordered from Bill N Y for $25, a very worthwhile buy.

Those'll give you an idea of what the various models look like. Anyway:

Pre-early '80s: All gaso, mostly pullers. No model designation usually

Regal: Gaso puller, gaso genset, ~28'-33', GM P-30/32 chassis, Workhorse chassis and others.

MCC Barth/MCC Regency: MCC Chassis, DD 8.2L, diesel genset; some with fiberglass body. 35'

Regency: Diesel pusher (Cat 3208T most common), diesel genset, Gillig chassis most common. 32-40', most widebody.

Breakaway: Diesel pusher (Cummins 5.9L, 160-230HP most common, except some '94s with DD 6.5L TD, 190HP), LPG genset. 28', 30', 32/33'.

Monarch: Diesel pusher (Cummins 8.3L common), diesel genset, Spartan chassis common. 34', 36', and 38' known. Widebody. Rare.

Sovereign: Diesel pusher (C 8.3L), diesel genset, Spartan chassis. Widebody. Rarer still. One seen: 36'