If the goal is to put a lot of movies in your iPad it may be a better idea to spend on a portable 1 or 2 TB SSD like the Samsung T5 or Sandisk Extreme, and the necessary adapter to move the files. I too use my 256 GB iPad mostly for videos, and the max file size for a 4K movie extracted from a UHD disc (lossless, remux) can reach 70 GB.
If I were to buy the iPad again it would make sense to get at least 512 GB, and rely on an external drive or a cloud service like Google Drive, where you get 15 GB free accounts (and sometimes you are able to create without SMS validation, restricted to a single cell phone and 2 or 3 accounts) or pay for storage, if I am not mistaken 1 TB costs 10 $ monthly. Over the years I created multiple free accounts and use an app called nPlayer to download the files or stream them. You can also share the contents of these multiple accounts with a single one, so using nPlayer it can see what each one has, without the need of the tiresome work of logging into all the accounts just to see the scattered contents (define the main account and share them all with it).
Besides, Google reaches the max speed for download and upload here. I think paying for Apple storage is overkill if you can buy an external SSD. How so? You pay 200 $ from 256 to 512 GB (899 - 1099 $) and 400 from 512 GB - 1 TB (1099 - 1499 $). While a 1 TB SSD costs 230, 250 $.
Just avoid getting an iPad which will barely have space for holding apps, games and a few videos, so my advise is to get 512 GB (256 may do but it’s very likely you will run out of space eventually).