The most popular production trailerable (swing keel) boats are up to 26. You've mentioned water ballasted MacGregor
. Have you looked at anything else such as Catalina
22 or 25? You've obviously sailed your swing keel Luger so you have something to compare water ballasted to non water ballasted. Which do you like the feel of?
If it were me I'd opt for the easiest to trailer and easiest to rig because you'll sail it more. I'd not got far off shore with a trailerable swing keel but many other sailors have.
Fin keelers on trailers require deep water to launch and bigger trailers meaning that you won't use the boat as much because they'll also require more effort to rig each time you want to launch unless you are going to keep it at a slip in a marina. Always a toss up.
I'd say an outboard on a boat up to about 30 feet is pretty much standard due to the space an inboard takes up and the ease in which a smaller boat can be pushed around.
Good luck in your decisions. You are getting a lot of good advice. Whatever boat you choose make certain the previous owners have taken good care of it and I'd advise that you get a popular for your area brand so that when it comes time to trade
or sell you can find a buyer.