I never had any trouble getting my Sea Pearl 21 to point well, if it wasn't getting rough and blowing sixes and nines. In a decent breeze without too much chop, she'd easily tack within 100 degrees if the sails were set, trimmed and handled correctly. The main trick was to recognize that the mizzen was a significant proportion of the total sail area, but it has to work in the backwind of the main (the forward sail). If the main is trimmed to sail as close to the wind as possible, the mizzen will have to be sheeted in more than is good for its contribution to forward drive, in effect "pinching" her. By giving her half a point more off the wind, sheeting the mizzen to achieve its optimum drive and then trimming the main a bit farther off so it didn't backwind the mizzen, she'd generally more than make up the lost ground by the gain in speed. This is pretty much true of ketches in general, as the late Phil Bolger would often point out.
Actually, that isn't just a theory. Once, sailing aboard our Menger 19 catboat (a very weatherly boat) in company with my son in command of the Seapearl, we covered the same four miles or so straight upwind--the catboat in three tacks, whereas the Sea Pearl needed five. However, the Sea Pearl covered the distance several minutes ahead of the catboat by giving up a bit of pointing to foot faster. Watching many other Sea Pearl sailors over the years convinced me that over sheeting and baggy sail shape due to suboptimal outhaul and vang tension were the chief culprits in cases of poor upwind performance. Expereince at the helm comes into it, as well; one needs to get the feel of keeping the boat "in the groove" when sailing hard on the wind, reacting to the subtle changes in wind speed and direction as you go in order to keep things moving along well.
The mizzen on the Southwester isn't quite as large in proportion to the main as with the Sea Pearl (more of a yawl, as John Harris points out), but I expect it'd be much the same thing as far as not trying to sail quite so close to the wind as one might with a high-strung sloop. As for balanced lug sails, my experience with my lug rigged Passagemaker Dinghy has convinced me that the rig can be quite weatherly once one understands what makes it work and how to set and trim it to get the best out of it. Seriously, that little boat has surprised me with her speed and weatherliness with Doug Fowler's masterfully cut lug sail.
As for rowing with the sails set, my experience with the Sea Pearl eventually taught me that there wasn't really much point to it for anything more than a few strokes here and there. The 21' boat was a handful to row as it was without all that distraction. With two modestly sized balanced lugs, it should be pretty easy to lower the Southwester's sails and bundle them off to the sides and out of the oarsman's way to allow effective rowing, and equally easy to reset the sails if the breeze comes back. In my Passagemaker, if I think she'd get me where I need to go better under oars, it is child's play to switch from sailing to rowing, even striking the mast altogether if it looks like a long row in prospect.
I think you're right about the motorwell. It would take up a lot of room, and is probably best left out if you haven't bought into the common fallacy that it isn't safe to venture out without one.
Again, I'm hoping someone with actual experience in the boats you're considering will chime in here to give you more insights.
.....Michael