What should I expect when using electrical equipment rated for 100V/120V at 110V
You can measure voltage and frequency with either a good-quality multimeter (e.g. a second-hand Fluke 77 on eBay

or a plug-in "Kill-a-Watt" type of meter. 

Cheap $5-$50 new no-name Chinese-made multimeters are usually not really safe for use on 230V



Personally, I doubt a 10% difference in voltage will be critical for any of those devices apart from the Japanese 100V items, that could overheat. n.b. EU supply = 230V+/-10% US supply=120V+/-5% so running a nominal 100V device at 126V might be cause for concern.



Japan has a mix of 50HZ and 60Hz supplies so I'd expect Japanese made 100V appliances to be happy with either.