Most probably by context and intonation (you definitely can't tell from the sentence alone).
If you want to make a distinction you can say:"אלה תותים טעימים" (these are tasty strawberries) and "תותים הם טעימים" (another way of saying strawberries are tasty, putting and emphasis on the are).
I don't know, for me adding "הם/הוא/היא" after the subject sounds unnatural. It's unnecessary, and I think it mostly comes as an attempt to replace the verb "to be" which is missing for a lot of people (especially English speakers). The only reason I would use it is in order to add an emphasis to the sentence.
Of course it's still correct, but as I said, the only way to interpret the sentence above is by context or intonation.
I personally feel that the most natural way to say "Strawberries are tasty" in modern Hebrew is "תותים זה טעים". (Though I think strictly speaking it's grammatically wrong). "זה" is used a lot for these kind of general statements - "ילדים זה שמחה" (Children are happiness), "מלחמה זה רע" (war is bad).