I switched from a 66 CC two stroke for many reasons and vibration was one of them though it seems some folks have figured out how to mount a two stroke without your teeth falling out after 8 miles at 30 mph.
I'm sorry but I just can't relate directly with all the vibration issues people seem to have, 50 some 2-stroke builds and not a one had any noticeable vibration let alone a fatiguing one.
Simple actually, I start with bikes that cost $170 and up, I only use SKyhawk motors, I use a custom 'muffler bracket' type front mount for nearly 360 deg hold, use the steel back mount bracket and pitch the cast garbage, never EVER try to put something between the motor and the frame like rubber, and cut that obnoxious hard plastic throttle grip off the barrel and replace both grips with BMX foam grips.
Sure, those among many others are a lot of extra steps and not free I take on every build but that's just how I build, if you can't ride it comfortable it's simply not a 'nice ride'.
I have a 26" cruiser with the four stroke 49 CC on it and love it. I go as fast as my two stroke and that is without any modifications. Doesn't vibrate me to death.
I like those HS 49cc 4-stroke Honda knock-off motors OK, it depends on the transfer case of course but the motor is sound.
There are pros and cons but all that aside it comes down to usability just like your vibration on a 2-stroke.
Those small 4-stroke are gutless low RPM wonders, a 2-stroke will leave it in a dust. 2-strokes however suffer from a loss of power at high RPM's and high R's is the sweet spot for 4-strokes.
Unlike a 2-stroke where you just need to pedal a little, you have to pedal a LOT to get a direct drive 4-stroke going, unless of course you have gears.
Gears change everything especially for 4-strokes if you do it right.
I built Big Red for my personal ride for awhile before I went on to my next different tech personal but I sure liked it.
49cc HS motor on a Sick Bikes 4-stroke shifter platform inside a Macargi 7-speed converted to a 3-speed internal Nexus hub back wheel bicycle.
Sure my HP 66cc Shifters would kick it off the line, but nothing direct drive could get far (100 feet or so) before I overtook them and then strolled away in front.
Just my personal experience with them, take it or leave it.