You can usually use this 3-striker tactic against almost any formation.
Except tactics that utilize 1 striker, 2 wingers and no central attacking midfielder. Fr example, 4-1-2-3 DM (4-3-3 Wide) and 5-2-3 Wide.
When you face those formations, use my other FM18 tactic: Suk Sam 4-4-2.
For now, I think this is the most overpowered formation on the full version of FM2018; using 5 backs and 3 strikers.
Just plug & play.
Suk Sam 5-2-3 ResultsHere are some results.
General team training : balance - average (in case of 2 matches in one week, lower this to 'low')
Match preparation : leave it to your assistant manager
Corner kicks : MCR or MCL
No opposition instructions (during match, you can set some OI's following your assistant's advice)