Brand new to Xcom universe, fallen into this rabbit hole- some perspective after 90 hours

Hi, as I am reading through the posts I like this place in the internet where you can leave the other bs and talk about favourite games and stuff :)

Recently my taste in games evolved strongly into turn-based strategic action ( or deck-builders), So I revisited Xcom ( my first one was Chimera Squad and I was bounced back from it).

After multiple load save actions I managed to finish the Vanilla campaign on the 2 level of difficulty and now I am playing WOTC on the third. It is fun, it is repetitive but the more hard the missions are the more satisfaction after finishing it.

going
Hence I have some questions about potentially planning my third playthrough (I currently killed all of the chose and I am casually flying around and kicking alien asses with my superpowered rosters and even don't need to save scum anymore.

What mods do you propose to make the third attempt more challenging ( I was thinking about the last difficulty or going Ironman ( where is this option?) - maybe this would be best before I use mods- or maybe there are mods already doing some changes in the playthrough or difficulty scaling to make it more linear ( I see the biggest challenge is to survive at the beginning- after weapon and armour modifications and getting a grip with some soldiers being promoted it is becoming easier and easier)

One last thing- I am Polish and I never got a Polish soldier- are they present in the game? We have some great special ops guys in our GROM (Thunder) unit