Re: My understand is there's not an "SLC write cache"
Well yes, where "cliff" = "still orders of magnitude faster than any hard drive, and competitive with SSDs from just a few years ago". How fast do you need your SSD to be? Most people could use one of those Intel 320 series SSDs from almost a decade ago - which I still do as boot & /home - and not notice if they got the 10x or more speedup possible from the latest and greatest.
If you regularly copy multi gigabyte files, or run an Oracle DB for fun, then yeah you probably want to make sure you don't run into the 88% slowdown.
As for "better off with a smaller or more expensive drive with a proper SLC write cache"...you already have that with this Intel one. You want one that's smaller, use only half its capacity (by leaving half unpartitioned) and you're fine, or you could buy one of Intel's that's twice the size for presumably twice the price, and again use half of it. The nice thing about using half of a drive is that you have some spare storage in case you ever need it in a pinch, something you don't have if you buy a smaller or more expensive one and use its full capacity.