The problem, if I can call it this way, is that it's an Accusim airplane, which means it has a special behavior both for the flight model and also the engine.
This makes things much more realistic, and of course much more difficult.
I've been using the T-6 suggested by Pete for several years until now. I was flying it in FSX first, then in P3D. That T-6 is extremely easy to land, unlike its real counterpart. You can land that T-6 in the sim in Darrington without any problems, but you won't land the Accusim T-6 so easilly. My guess is I'll probably need several tries before I can get it to land there... And I'm not sure I have any chance to succeed...
I definitely recommend this addon, for anybody who wants to know how a T-6 actually performs. They have added a bit of "magic" to implement a high-fiedlity ground behavior. The T-6 is known to be very dangerous to land, due to the risk of ground loops, and the Accusim plane reproduces this very well.
And the engine management and sounds are also perfect, as expected from Accusim.
Concerning the P-51, I've been flying the default one for a long time before I switched to the Accusim one. The flight characteristics of the default one are not that bad actually, the general behavior in flight is believable. However, the behavior upon landing, especially after all wheel are on ground, is a bit different. The default plane is easier to bring to a stop. And the engine won't mess with you