Yes, have WPA2 personal AES (I found that allowing TKIP/AES was unreliable) and a max length, fully randomized key.
https://www.grc.com/passwords.htm
And my immediate advice would be NOOOO! It is such a pain to type (and I thought I'd only ever have to type it once, doing a cut & paste from a text file subsequently).
The "password haystacks" article is also interesting, in showing how the total search space expands - NOT the actual strength of a password.
Looking at the analysis, a 12 character, upper/lower/numeric/symbol mix looks pretty robust (estimated 1.74 centuries vs massive cracking array).
Using just lowercase alpha, it still takes only 17 characters to reach that level.
So long as the key is not a common dictionary word or common non-dictionary key, then the faster attacks are neutralized - since the most classic is using a rainbow table of common SSID names hashed with common passphases, it also helps if the SSID is not the default, or a common one like "home".
Using just lowercase (far easier to enter on a device that does not have a real keyboard) seems wrong, but a random sentence from a random page in a book, would not be that bad - best to collapse all spaces, as it some devices handle spaces incorrectly.