I'll tell you what I have, and maybe it'll help you find your way. I'm still on FM20, mind you.
1) Base Tactic: 4-3-3. SK-S // WB-S, CD-D, CD-D, FB-A // CAR-S, AP-A, CAR-S // IF-A, IW-S // PF-A. PIs: on CBs and GK to pass shorter; ST can have more direct passes but I don't see many changes). Positive Mentality, Be More Disciplined, +1 Width, Counter-Press, Counter, Distribute to CBs, Higher LE, Much Higher DL, Pressing Maxed, Prevent Short GK Distribution, Tight Marking. Opposition Instructions: Tackle Hard on all defense and DM, Tight Marking on CAM. Show weaker foot to STs.
2) For tough matches: FB-A to WB-S; Counter-Press to Regroup; Cautious Mentality; Pass into Space.
If other team has 2 strikers, I also change the distribution to full backs, flanks or playmaker (depends on how they are playing)
3) Holding the lead: Almost the same as tough matches (without pass into space); sometimes I switch Counter to Hold Shape or leave unselected; Waste Time on the middle from 75+ minutes; Full Waste Time from 85+. Sometimes play out of defence, sometimes lower tempo, sometimes drop the lines a bit (this all depends on how the game is going). Be careful with their formation.