Hi

Dalk is more formal than miskien, and should probably be used in writing, rather than using the word miskien.

In a formal letter, I would rather use the word moontlik, which can be translated as the word perhaps or when something is possible.

I'm no expert, but I thought I saw a pattern during my studies. As odd as it sounds, it seems as though "Miskien" goes at the beginning of a thought, or as a stand-alone statement, and "dalk" seems to fit well in the middle of a sentence.

For example:

"Miskien jy kan my help. Ek weet niet hoe om dit te gebruik."

"Moenie bekommerd wees nie. Jy sal net dit gebruik dalk vier of vyf kere in 'n jaar."

You'll be understood no matter which word you use, but that's my two cents.