Learn English – Most used vs mostly used

Short of consulting other resources or data sets that show English word usage frequencies, the long-term answer is to read as much as you can. As with any language, English speaking children go through school reading books with many words they do not understand and often don't take the time to look up unfamiliar words in a dictionary. However, after so much exposure to words, if they were to see them as synonyms in a thesaurus for a word they did know, they would intuitively know which words they had encountered more often in their life and therefore which ones were more likely to be idiomatic or correct. You can replicate this experience, to a certain degree, by increasing your exposure to English that contains words you don't understand but can get a sense of with context clues.

As for your examples, in American English, the words "attractive" and "charming" would be the most common and relatively neutral in connotation. "Attractive" is by far the most common, and thus would be the most likely to use in a conversation. The word "fetching" is not common in American English usage, and the word "bewitching" bears an additional connotation that a person's beauty is so intense as to deprive its beholders of self control.

In US English, there's really no good idiom but a casual way of expressing that in speech might be,

For activities:

They all sound good, but I'd rather X.

For things:

They all look good, but I like that one -or- X