It seems that IDA Pro with version 9.3 finally reached maturity level of the Visual Studio -- you're using old version not because you like it more, but because it doesn't have UI lags 😬
@anparker It seems that it was font rendering issue in Qt: I fixed those lags by changing command window and hex view font to Consolas. For unknown reason, it picked up some terminus-alike raster font by default (which is weird because I don't even have it installed, it's a clean Windows box)