I usually go with "balanced" mentality when I try to be more pragmatic i order to change the style of play depending on how it's going.
"a bit easier"? You're having a laugh.... Attacking tactics are by far easier than defensive once... Just look at the tactics that win the most titles in the game, the attacking once, and by attacking once I mean the gegenpress and tiki taka.
Btw, it's not the underdogs that are the problem. When I try to do a Mourinho and close a game against a strong side I just end up seeing highlight after highlight and eventually the AI will score, they always do. No matter what I do.
For an example, when I took charge of Atletico de Madrid I played home against Barcelona, not a underdog team, I then tried to do as Mou', Conte and Diego would do in those games.
Play with a defensive mentality, low block, lower LoE, defend narrow, high press(I feel like you need to press in the newer FM-games, not pressing tends to give the AI more space and will end up in a lots of goals for the AI), direct play, higher tempo, be more disciplined, waste time, play for set pieces, counter, somtimes I use counter-press, mark the best players in Barcelona.
I usually tend to have 6 players on defend, 3-4 on support and 1-2 on attack. But what ends up happening? I'll tell you. You end up seeing Barca create ccc's constantly and they will end up scoring and you'll hardly see any counter-attacks from your side at all.
The formation I played with was 4-4-2, as Atleti does in real life.