There is a lot of info' floating about regarding Modified and Pure sine wave inverters. I am not a technician, nor an expert in any sense of the word.
I just switched us to a new Outback VFX inverter [which is "pure" sine wave] after using a Trace [Xantrex] modified sine wave inverter to power the ac loads in our house for well over 20 years. My wife works from home, with computer stuff, and our computer equipment includes five computers, three flat-screen monitors, late-model laptops, printer, etc. In addition, we have the usual collection of vacuum cleaner, clothes washer, Vizio flat-screen tv and etc etc.
In all these years, we have had zero problems with modified sine wave. I do not discount those who advise to stay away from such inverters. All I can say is, in our experience, no trouble of any type I've ever witnessed. The only reason I switched to the Outback is that I have gone to a different battery chemistry which I anticipated the Trace would have trouble with. The input voltage allowed for the Outback is higher than that listed for the Trace....
I understand, from forums such as this one, that Xantrex [formerly Trace] is now having its equipment either manufactured or whatever overseas [read: China??]. I do not know that for certain, just what I've read. Whether the quality has decreased due to this, I have no experience to say one way or the other. Just something for you to check out.