Well...you may regret having asked these questions - but here are some definitions and some highly personal opinions.
A genuine "plank-on-frame" model replicates, or closely replicates, the actual methods used in the construction of the prototype ship. The frames (known to landlubbers as "ribs" - but old salts will tell you the only thing that has ribs is a barbecue) are reproduced to scale in terms of both dimensions and spacing. That means that, in the case of a good-sized ship of the seventeenth, eighteenth, or nineteenth century, there will be more than a hundred of them, and the spaces between them will be about the same as their thickness. The hull of a plank-on-frame model is hollow, except for the decks and other features of the real ship. On many such models (the most famous being the so-called "Admiralty" or, more correctly, "Navy Board" models), the planking is omitted from large areas to show off the workmanship of the framing.
"Plank-on-bulkhead" construction is a simplified version that replaces the scale frames with bulkheads - thwartships partitions that are cut to the outlines of the ship's cross sections. The bulkheads are spaced much further apart than scale frames. In good kits they're made of basswood or some other medium-to-hard species; in lesser kits they're made of plywood. (Since you're a carpenter, I won't insult your intelligence by explaining what's wrong with nailing planks to the edge of a piece of plywood.) A good plank-on-bulkhead model, if it's completely planked, is externally indistinguishable from a plank-on-frame model - though internally they're quite different. In the hands of a good modeler, the plank-on-bulkhead system is a good, time-saving method of construction. In the hands of a not-so-good kit manufacturer - well, more in a minute.
"Double-planking" is a trick original conceived by certain European kit manufacturers to compensate for bad design, poor materials, and unskilled customers. The idea is that the modeler first planks the "armature" of bulkheads, keel, etc. with some soft, coarse-grained wood, and then applies a second layer of a better-looking species (typically walnut in the European kits). Despite what the manufacturers imply, this is not authentic. It does, however, turn the model's hull into a sort of "monocoque" structure that doesn't rely entirely on the bulkheads (which the manufacturer usually has sited too far apart) for its integrity.
The other common form of wood kit is the "solid hull." In this system the kit manufacturer (usually by sub-contracting with a furniture company that has a big lathe) provides a piece of basswood (sometimes pine or poplar, but basswood is by far the most common these days) carved to the shape of the hull. I some ways this is the easiest system for the kit builder. Such features as the keel have to be added on, and the bulwarks generally have to be reduced to scale thickness, but the basic shape of the hull is present when you open the box. The drawback to the solid hull is that it has no points of reference from which measurements can be taken. You have to draw a centerline on it, for instance, without really being sure where the center is. In a good kit, that's not much of a problem; in a bad one it makes it almost impossible to build a symmetrical hull.
Most of the sailing ship kits marketed today come from Continental Europe, and, by the standards of accuracy typically expected from readers of
Fine Scale Modeler,
are overpriced junk. The materials are inferior, the construction methods irrational, the fittings usually out of scale, the draftsmanship of the plans mediocre, and the "research" ludicrous if not downright non-existent. They command hideously high prices, due largely to their appeal to interior decorators. I used to work at a maritime museum that sponsored a fairly prestigious ship model competition every five years. The word in that contest was "don't bother entering a model built from a European kit; the judges won't look at it." That may be a little harsh, but I've yet to see a Continental European kit that was worth bringing home from the hobby shop. (One semi-exception seems to be the line made by the British firm Calder Craft. I've never looked at one of those kits, but on the basis of some write-ups in ship model magazines they look much better than the Continental ones.)
Two American companies, Model Shipways and Bluejacket, make some nice wood kits. Most of them are either solid hull or plank-on-bulkhead. They're based on sound research, the fittings are reasonably close to scale, and the materials - generally basswood, brass, and Britannia metal - are good if not great. (Veteran ship modelers don't like basswood; they lean toward such materials as cherry and pearwood, which are, from the kit manufacturer's standpoint, prohibitively expensive.)
My personal suggestion regarding a subject: start with a small vessel on a big scale. The Model Shipways Chesapeake Bay skipjack
Willie L. Bennett
is a beauty. It's plank-on-frame (to the extent that a skipjack can be said to have had frames), with a set of plans and an instruction book that provide a virtual course in basic modeling. The same firm's
Emma C. Berry
and "Virginia Sloop" also look like nice beginner's subjects, though I don't have first-hand experience with them. Bluejacket's New York pilot schooner and yacht
America
also look good for that purpose.
Too many people start with a
Constitution
or
Victory.
. Those folks generally drop out of the hobby, due to the phenomenon of the learning curve. By the time they've worked on the model for a few years, with no end in sight, the work they did during the first few weeks looks awful to them. My suggestion is to pick a small vessel in a large scale and spend a few months having fun with it - and learning. If the experience is pleasant, pick something more demanding for a second project.
There's an unfortunate shortage of good books on ship modeling for novices. Two that I can recommend are
How to Build Great Ship Models from Kits,
by Ben Lankford, and
Period Ship Modeling
, by Wolfram zu Monfeldt. (I may have garbled the titles a little.) On a slightly more sophisticated level is the Nautical Research Guild's
Ship Modeler's Shop Notes.
One final observation. Serious, experienced ship modelers have reservations about wood kits in general. This branch of the hobby is quite different than aircraft or armor, in that the kit manufacturers haven't come close to catching up with the scratch builders. I used to work in a hobby shop, and repeatedly angered my employer by offering the following suggestion: if you want to build a good model of a sailing ship from a kit, stick with the best of the plastic ones. If you really like to work in wood, build from scratch. It's not as hard as you may think.
By now you're undoubtedly sorry you asked the question in the first place. I feel obliged to repeat my opening caveat: these are personal opinions. They are, however, based on about 45 years of model building, and I don't think many experienced ship modelers would disagree with them.
Good luck. It's a terrific hobby.