First of all, I'm running three OSes on that SSD. Second, I have a virtual machine on at least one of them. Third, I haven't used anywhere near the whole 512 gb; the three OSes use about 300-350 gb together, but that includes all of the free space on their partitions. I could easily cram them into 256 gb if I had to and for that matter, I could get rid of Linux Lite. The Ubuntu partition has a lot of music and photos on it. And yes, there are undoubtedly cached files I could get rid of.
Question is, why bother? If I saw a laptop I wanted that came with a 256 gb SSD, I would buy it as long as it isn't soldered on. The only laptop I'm considering with a soldered on SSD is the current model Dell xps 13 9315, and it comes with a 512 gb SSD. One of Best Buy's marketplace sellers has last year's 9310 refurbs in excellent condition. They have two configurations with touch; an 8gb RAM 256 gb SSD for $899 and a 16 gb RAM 256 gb SSD for $80 more. If I was to buy this one, I would pay the extra $80 for the extra RAM. I would then probably upgrade the SSD, but at my leisure. Ironically, the same reseller has the newer 9315 refurb in excellent condition; it comes with 16/512 for only $899 but of course this model has the soldered on SSD. Not that I would ever need to upgrade it; my worry would be if it malfunctions down the line.