Regarding Shayim Mikra V’Echad Targum: if I do not understand Aramaic, is it still worthwhile to read Unkelos, or is it preferable for me to read another commentary that I understand?
It is still worthwhile to read Unkelos. In addition, you should supplement as much of Rashi as possible, in addition to Unkelos.
Unkelos was the original “commentary” given at Sinai. In addition it covers every single word of the Torah. Over time when done carefully, one will usually begin to understand more and fulfill this mitzvah properly. There are Aramaic/English dictionaries which could be helpful. Even a few words a week soon adds up and will be very helpful.
Ultimately, if only one commentary can be said, there is a dispute if to choose Rashi or Unkelos, see Shaarei Tshuva O:C 285:2 who brings both opinions, and notes that according to the kabbalists one must not skip Unkelos. See ibid. the Biur Halacha who discusses this issue at length and does not reach a conclusive decision, rather recommends doing both.