I've gotten the basics of aircraft design with FAR installed down (CoM ahead of CoL, landing gear close behind CoM, check stability derivatives in the FAR analysis screen, etc) as well as the basics of designing low-drag aircraft (area ruling etc), but I'm interested in any resources or information about optimizing aircraft as much as possible to perform well in terms of maximum speed and altitude. What kinds of features should a plane have to perform better in those regimes? I'm currently working towards sort of an X-plane program in my career mode install (i.e. building faster and faster planes leading up to a spaceplane), and I'd like to optimize the aircraft as much as possible. I'm working with FAR and RSS in terms of mods, so the difficulty is greater than stock.
Also, how can I make my high-speed aircraft perform better at low speeds and altitudes? I understand that it's difficult to do that, since getting an aircraft to perform well over a wide range of speeds and altitudes is very difficult, but I'm currently having issues with my latest X-plane stalling at speeds below 120 m/s, which makes landing a pain. I typically end up trying to come in as slowly as possible (in the vertical direction) at 120 m/s and then flaring/cutting power, but this just leads to me bouncing down the runway several times, flipping over, and destroying the plane.
I'm not posting from my computer with my KSP install on it, so I can't post the craft file at the moment, but I will as soon as I get back to my KSP computer. Basically, it's a single-engined delta wing aircraft with no horizontal tail or canards, powered by a single J-33 jet engine. I essentially attempted to get it as close as possible to look like the F-106 (pic included). It performs pretty well, achieving a maximum speed of almost mach 2 and a maximum altitude of ~20 km on a 20 kN engine (the engine only produces a fraction of its rated power due to airflow restrictions). However, its performance while landing leaves a lot to be desired.