I think the only difference with the new version is the ability to change the lighting tone and more storage. I would 100% recommend an e reader over a tablet, I tried to be cheap and bought a fire tablet instead of replacing my dropped in the bath* Kindle during lockdown and found I couldn't read in the garden because of the sun.
If you have the money to spare for the newer one get that just to have the most up to date for battery life, otherwise an older paperwhite will be fine, the good thing about them is there isn't much technology so they last until you break them yourself! (I also wouldn't pay more for ad free, the ads are only on the lock screen and sometimes they're useful for finding a new book)
*don't quote me but I think the new ones might be waterproof, or maybe i'm thinking of the super expensive ones.
