A suggestion with transformers. Most of the ones you buy to take overseas are auto-transformers. If you are plugging any electronics into them, make sure that the polarity is correct. You can buy a cheap tester similar to this one at any hardware/electronics store. Most electronics today are multiple voltage, so this may not be an issue for you, and polarity isn’t an issue for appliances and the like. However, an auto-transformer that is plugged into a mis-wired outlet can develop dangerous voltage to the case of the transformer, so it’s not a bad idea to check it out.
At least for electronics with switch-mode power supplies, even those that aren’t universal input, this is pretty much a non-issue, or at least I can’t picture any scenario where a power supply would malfunction at a slightly higher (or lower) voltage unless it was **very **marginal in the first place, same for line frequency. If anything, a higher line voltage will usually increase the efficiency of a SMPS since for a given load, primary side current (mainly through the switching transistor(s), a significant source of loss) will decrease (loss is proportional to current squared, so halving current will reduce losses fourfold (switching losses do increase but not by as much), the reason why some 120 v only equipment use voltage doublers).
On the other hand, I have seen some very old equipment, such as a Tektronix scope (1960s?) which had vacuum tubes and germanium transistors, that actually had multiple taps on the main power transformer to select voltages to the nearest 10 volts (100-110-120), presumably because the power supply wasn’t regulated, at least not completely.
Anecdotally we’re usually pretty careful about using a transformer with our .jp appliances in the US, but we have friends who are not. Never heard of anything blowing up. Our worst problem was the time we forgot to use it on the takoyaki maker, and it did get hotter than usual, leading to them being done on the outside, but not quite on the inside.