Just as an example, imagine a set of blades designed for tsr 6. If you aim to reach cut in with the blades running at tsr 6 or more you find the blades speed up rapidly to cut in. If the alternator is vastly too powerful the blades will not have the power to hold this tsr and the blade speed will hold constant and wind speed rising will mean a fall in tsr. This would result in operating at near constant speed and the tsr would fall constantly. There would be an increase of power as the tsr falls from above 6 down to perhaps tsr4. beyond this the power may remain fairly constant.

You would probably not see any speeding up and slowing down, it would sit at near constant speed.

In real life with any reasonable alternator efficiency you will never reach that level of stall if your cut in is at design tsr or above. Beyond cut in you should see a fairly steep rise of power but that will become less steep as you get down below ideal tsr.  How far you go beyond cut in wind speed before things levels off depends on the alternator efficiency. If the alternator is too inefficient to bring the tsr below 4 at any point the blade power will not level off and anair gap alternator will increase power until it burns out. Iron cored alternators can reach a constant power output condition due to reactance if conditions are right and the blades will run away while producing constant power (not to be confused with stall).

This graph shows the effect very well. It is for a 6ft prop with a powerful alternator.
Connected directly the thing stalls badly. With some resistance to reduce the alternator efficiency you see a fair improvement in power out even though the alternator is less efficient. This is normally the best compromise with direct loading.

The to curve shows what happens when you match the load to let the prop run at constant tsr without lowering the alternator efficiency. You then get best prop and alternator efficiency with no trade off between one and the other.