So you agree that the voltage fluctuation is harmless? That's what we concluded, so I was more concerned about lightning and I do remember you recommending a "whole house" surge protector for that.
Was just wondering if there is any easier way
Those devices claim to protect from transients that typically are not destructive. A Brickwall or Surgex will stop what three miles of sky could not? Not likely.
How often does a destructive surge exist? Typically once every seven years. A number that varies with venue. To say more would require, for example, a neighborhood history for the past decade.
Spend that much for an expensive solution plug-in solution. Or spend equal or less money for a 'whole house' solution.
Which ones are good? Numbers. For example, if power factor is a problem, then a line conditioner may list a number for power factor correction. If noise is a problem, then it will list filtering in dB for various frequencies. If voltage regulation is required, then it will list that regulation with numbers. If harmonics is a problem, then it might list something like %THD. If galvanic isolation is required, then numbers define that isolation. But no line conditioner does everything.
But again, no box solves all anomalies. That magic box is to often recommended when an anomaly is not first defined. Or when hearsay is sufficient to make a blanket recommendation.
Lightning (or something equivalent such as a car crashing into a telephone pole) may create a typically destructive anomaly. No adjacent box claims to protect from that anomaly. Again, the numbers.
.......its forty bucks, so if it gives you peace of mind....worth it