Assalam u Alaikum ...
i accidentally visited PW after a long time today; and yes, 2-Stroke wins the world that's why I'm on this thread too.
To answer your questions, I'd add and share my experience;
Intro: I own my dad's 1979 Kawasaki 100 Sports G7T and that is the only bike I own, and also that is my daily runner; condition now is its quite weak on top end after 2 years of full throttle usage everyday, still able to smoke away any CG125 of the day;
--> My daily running exceeds approximately ~35 kms (including local road, GT Road and Isb Highway); I never had any problems in recent times;
--> As far as vibrations are concerned, depends on your engine condition, like I know my bike is running on a not properly aligned crankshaft, it does vibrate on 90+ kph; BUT.. for a properly done GTO125 to vibrate on seeds exceeding even 120 or 130, I won't buy this stance..
--> Throttle locking syndrome: to better understand how does it destroy an engine, I played Need For Speed Drag Race; which visually instructed me how we destroy an engine be it a 4T or 2T; theoretically 2T would blow early as it revs quicker; but in the real world, going in your top gear you almost never achieve full engine cycles i.e. 11k or 12k rpms.
What I mean to say is if you keep running your bike on 11k or 12k rpms in any gear for long time, you'll definitely damage it. but if in top gear you're doing ~9k rpms you're good to go. (PROVIDED THAT your carb jetting and your auto lube systems are working perfectly fine).
--> NO one would have experienced spark plug failures as I have ... When my bike had an old carb with poor mileage i.e. ~18 kmpl, I experienced worse plug failures, but now with a new and perfect running carb and good running super lube system, I never have to undo my plug. P.S. I change it almost every 10k kms;
--> Spares are much expensive; and a really p.i.t.a to find; I know this feeling because I have been collecting parts worldwide;