OP, here is my answer to your original query, FWIW:
Upshifts: I always use the clutch, and I use a light amount of preload on the shifter. I learned the preload shifting from a racer who taught me to ride, and I think it produces very quick, clean upshifts.
Downshifts: I always blip the throttle to rev-match the downshift as perfectly as possible. I find that if the engine is already climbing in RPM, even if I'm not perfectly at the right RPM yet, it will make the transition a lot more smoothly.
With respect to shifting style, I try to make my shifts as smooth as possible on general principal: I want to destabilize the bike as little as possible. The suspension is doing a lot when you have it under load (accelerating, braking, navigating unevenness in the tarmac, or under compression from hard cornering), so I want my shifting to be as quick and smooth as I can make it.
An example of this is if I am coming up on a second gear corner, but I'm currently in fourth gear. Usually I will try to make two very quick downshifts as I roll on the front brake. The downshifts act as a braking force on the rear wheel and by the time I have finished braking, I am usually in the right gear to start rolling on the throttle just as I hit the apex of the corner. This comes from wanting to break cornering into stages: Set my entry speed, set my turn in entry, do my turning as hard/early as I can, and get back on the gas as early as possible. Up or downshifting, if its rough, can unsettle the suspension in ways that will carry into the next phase. For example, if I have to drop two gears and I do it roughly, the bike can be still recovering from that as I begin hard braking and that sucks.
I don't like to get into the clutchless shifting debate. I have done a bit of it, it seems ok, if it saves you milliseconds on a fast lap time (or even if its just fun)...more power to you.