If North Carolina is any indication -
Once the GOP loses control, they'll quickly shove through new House/Senate rules that denude the power of committees and majority leaders. The NC legislature stifled the governor's powers last year because a Democrat won.
If Kansas is any indication -
Once the GOP loses control, they'll slash funding to education, healthcare, and welfare just to say they finally did it (Been promising those a long time), and insist these are balancing the budget and enhancing growth (Note "growth" has been the GOP's favorite economic talking point lately).
If Wisconsin is any indication -
Once the GOP loses control, the lame duck session will slash the "deep state" aka the civil service corps. People who've built careers and put kids through college will be unemployed. A whole chain of continuity from lowly GS-5's and up will have their pay and benefits slashed. This will bleed the civil service dry and permit a wave of new government contracts with companies tied to GOP office holders' interests.
If Oklahoma is any indication -
Schools nationwide will slip to 4-day weeks as teachers move to Canada for better pay and QOL.