VOICELESS ASPIRATED VELAR STOP [kʰ]
VOICELESS UVULAR FRICATIVE [χ]
Kaf with dagesh is pronounced like English "k". Kaf with rafe, which typically occurs after vowels, is pronounced with the back of the tongue low in the throat as in the "ch" in the name of the composer "Bach". For those familiar with Arabic, it is pronounced like the letter khā (خ). For kaf with rafe, it is important to allow air to pass through to make a fricative sound.
SOURCES AND FURTHER READING
Khan, Geoffrey. 2020. The Tiberian Pronunciation Tradition of Biblical Hebrew. Cambridge: Cambridge and Open Book Publishers. §I.1.11.