That's pretty accurate in my experience. Every time I find amazing tabs, they feel to be around 200ug in strength.
These days, tabs I buy off the street or DNM, that are advertised as 100-110ug, feel more like 50-60ug.
Tabs in the 90s or earlier were typically dosed quite high, 100-200ug or even higher.
Also, in my opinion it's a myth that there are any special types of tabs out there. Different brands, needlepoint, etc, all that is bullshit.
There are certainly impurities which can add side effects to trips, but there's no real trick, different types or magical tabs out there. Boils down to dose, impurities and nothing more.