Dont forget the lossless compression for RAW files is very effective and results in no loss of quality or speed of processing. File sizes are about 30MB and I use them all the time in conjunction with full quality jpegs.
I use a 64GB card.
Enjoy your XS-10, I have had mine since September 2020 and love it.
Well, no. Or maybe. It depends on things you can do now and on keeping your options open. On its own, there is nothing wrong with the 256GB cards, they are fine.
That size should let you put over 4000 raw files on it before you need to move them over to your computer. Or roughly 3500 raw and jpeg files if you are saving both at once. However, if you get several smaller ones, you can swap them out if you are photographing an event, so that if something bad does happen to a card, you have not lost everything. Also, the smaller sizes usually are less expensive, so you can buy the faster ones for the day you decide to try recording videos — video need the higher speed cards, ones that are just fine for images sometimes have problems with video.
Unless, of course you are intending to start recording videos right now and need the space. Or the place you are getting them from is having a sale on the larger ones.