The eyepiece choice will depend (at least) on which galaxies, how you like the surroundings, and the quality of your sky (seeing and darkness).
You may want a large true field (combination of focal length and aparent field) to see some big galaxies like Andromeda, M33, M31. Also to see groups of them like M81/82, Markarian's chain...
If you observe from urban polluted skies, you may prefer high magnifications (even 1 mm exit pupil of less!) To increase contrast (up to a balance).
Large, frontal galaxies may call for low large exit pupils (low magnification, independently of the true field). This is if the pollution allows. I can't see M101 or M33 from my backyard.
I guess galaxies aren't or won't be your only interest. Plan a good set of eyepieces rather than one for galaxies. A good set will cover all your needs and do >95% of what a "dedicated" eyepiece could do for its specific target. Dedicated eyepieces are more usual for planets, but some have favorites for faint DSOs.
Once you have a set, experiment to see which one is the best for the any specific target. It won't be necessarily always the same. One day you may focus on the galaxy and nothing else, and another you may want the full panorama around.
Edited by sanbai, 20 May 2020 - 06:12 PM.