we've seen so many TOS-era Andorians in film and comics with antennae at the rear of the head that I tend to imagine there are different ethnic groups of Andorians with their antennae positioned differently. Although when I imagine a TOS-style Andorian, I assume the antennae can move ENT-style.
Same here. My first ever fanfic addressed the TOS/TMP differences as two sub-species, and of course now we have Aenar and lots more antennae variations (ST IV, TNG, ENT). And if an Andorian has been featured in cover art (Thala, Shar, Thriss) then I'm happy to go with that antennae configeration for that Andorian.