Things I would avoid:
Avoid compact cars - Mazda 3 is the limit, Mazda 2 is too small, Honda Civic is the limit, Honda Fit too small (simple physics in a collision with other vehicles, the vehicle with more mass is safer for its occupants);
...
Bigger vehicles tend to be safer to crash; smaller vehicles tend to be safer to drive (more mass == more momentum at the same speed, and quickly becomes a liability if things are going pear-shaped). Also, saying "I want to put my inexperienced driver in the biggest vehicle possible to make them safer in a crash" is a bit selfish from a societal standpoint, as it transfers risk to the rest of us, and we know (statistically) that inexperience drivers are more likely than almost any other group to crash.
The potentially problematic handling is exactly what makes them an excellent (albeit getting hard-to-find) learner's vehicle. An underpowered 2WD pickup requires developing a driving skillset that most drivers lack, and it strongly encourages treating driving as an actual activity, not just as a way to get from point A to point B. In slippery conditions, RWD (and a frontward weight bias) means that you're far more likely to make things squirrelly by overenthusiastic throttle use, rather than by developing understeer entering a corner. While both are potentially terrifying on the interstate, at lower speeds on secondary roads, I'd much rather have the ass end of the vehicle kick out on corner exit than have the front end decide to continue straight on entry. Sticking with something relatively underpowered requires thinking further ahead, which is a great skill to develop for general driving safety.I saw and still see no need to inflict my kids with the handicap of not being able to bring more than one passenger, and yes small pick-em-up trucks will take some learning to control the rear-wheel drive traction, with a light rear end, handling can be problematic with the back end trying to pass the front end when slowing down around icy corners.
And you can take two passengers in a standard cab or four in an old xtracab, it just won't be comfortable...which translates to better vehicle longevity because your friends won't designate your vehicle the road-trip chariot.
IMO, the biggest benefit of the high-performance course—or whatever other method you use to teach the same skillset, whether it be time with a parent in snowy lots, SCCA stuff, or intentionally looking the other way when they go out driving in fresh snow and come back with scuff marks on the bodywork—is that it encourages that "driving is an activity" (or even a sport) mindset. All else being equal, people who are clearly disengaged from driving and bored scare me far more than those who are trying to corner at double the advisory limits.
I'd also advocate for something cheap and near full depreciation so that, should the learning process involve crunching, scratching, or other unpleasant noises, the financial impact isn't so bad, and so that you don't feel a need to keep full coverage on the vehicle. If it needs a little more maintenance along the way, that's not entirely a bad thing—keep the kids involved so that (unlike some of my friends) they understand that there's a lot more cost to operating a motor vehicle than just putting gas in it.
Real old-fashioned standard transmissions are the best, 2nd best is regular automatics. Dual clutch transmissions are not so good if you do a lot of stop and go driving and want to keep it for a long time. CVTs are getting better, but most still have a lot of room for improvement. Don't buy a Nissan with a Jedco transmission.
Agreed 100% with the first part; I lack the experience level to answer the second part definitively.