drgondog
Major
I always thought that automatic LE slats were for slow speeds, not all speeds and definitely not at high speed.
As for the high AR of the 262's wing, it would certainly have a lower induced drag (but a higher parasite drag). However, higher AR wings have a lower roll rate and putting the heavy engines on the wing doesn't do you any favours on the roll rate, only helping to slow it down.
The best place for the engines is in the centre of the plane, no question and it's also causes less drag. I believe the Russians instead of copying the 262 came up with an aircraft which had two engines in the fuselage because of the reduced drag.
This bit is a guess on my part, but my guess is that the LE slats were to assist in the problem of loss of lift that happens with swept wings at slow speed. With a swept wing the airflow tends to be 'swept' to the wing tips instead of going straight over the wings. This causes a loss of lift at slow speed and one of the things that the LE slats will do is assist with the slow speed handling.
The 262 was built for speed not agility and the Germans would have found this problem out in tests, had considerable experience in LE slats and would have known how to address the problem
Glider, I can't speak definitively for Mtt but you are 100% correct with respect to functional reason for LE slats on F-86 - stability at low speed (as in final approach) for swept wing config. The MiG15 solved that problem with large wing fences to assist flow in straight (more or less) flow over wing.
I would also believe the drag would be higher for two nacelles than for an engine imbedded in fuselage - which is a primary reason twin engine fighters ALL are designed that way. I'm really having a hard time recalling a fighter with T/E imbedded in (or suspended) wing that started design after 1950.
That said, boundary layer control into a 'cheek' inlet has always been a strong focus for aero guys - particularly for high transonic to supersonic flow in which the mach (and shock wave angles) change significantly.
Compressor stalls were harder to prevent than a nacelle config engine mount.
I suspect (without proof) that the reason for the two engines on the Me 262 and Meteor was that no single engine was of high enough thrust at time airframe design started, to give the airframe the hoped for performance... and that the P-80 was the first that had an engine design on the horizon to cause Kelley Johnson to go with imbedded fuse engine.