well most things the government releases is mandated by law anyway, but there is discretion of course. For example there were a number of gimmicks that the Bush Admin used that the Obama Admin stopped (
see NYT article from 8 years ago). I suspect we may see those practices and other forms of creative accounting work their way in.
As for the GOP controlled congress, they have already changed rules for the CBO to use rosy scenarios and to hide the worst effects of repealing the ACA, so I'm not so sure they are the place to look right now.