Pay - expect to be mapped to their levels, and your pay related to that level. Not much flexibility unless you are promoted to the next level after performance review. So make sure mapping is done fairly. They would usually use your CTO and other tech leaders to help them map.
Layoffs - law probability, but with each perf review 5% is expected to get less than Meets All - and those are candidates for departure.
Politics - it’s terrible. Try not to let anyone from MSFT join your team for as long as you can - or interview them ferociously and gather references from several teams that they worked with before, to make sure you are not getting a surprise. Some of the transfers from MSFT to our team had previously known HR issues that we were not aware of but later on got hurt by.