Some special prayers in the mafatih al-jinan specify that you are supposed to pray them in two rakat units, but other prayers like this one (to be done on Fridays in Rajab) don’t say do it in 2 raka’at units, they just say it’s a 4 rak’at prayer. So am I supposed to do these ones as one long special prayer of 4 rak’ats (for example) or split them into 2 units as well?

All Mustahab prayers are done in 2 rakat units