afaik, you don’t specifically need ReFS to use Storage Spaces, but some features may not be available or work differently depending if you have the ReFS enablement.
For example it sounds like if you are using performance tiering, if you have ReFS, migration between tiers is real-time, but if you only have NTFS, migration is done via some daily batch processing. if i recall correctly, pro for workstations gets you ReFS but Storage Spaces is available at a lower level, but i don't know what the cutoff is. i get the impression this has been a bit of a moving target, and there's weird things like i don't think there's a gui for it in windows 10, but it's there.
your point about the complications of having large data sets is good and i was actually going to make a comment explicitly on that topic generically because this applies equally if you're using storage spaces, or raid....
folks should be aware that whenever you start bundling your storage into bigger chunks, data management gets more complicated, takes longer and you have more restrictions.
for example, if i have four 10tb hard drives, if i want to add some space, i can just add a another drive and start using it. however, if instead of those four 10tb hard rives i have 40tb of raid space, for one, now i have a LOT more data which will take a lot more time to move that data off that space if i need to, AND, if i want to re-do that raid to change it's configuration, i have to get ALL that data off, so it means i have to have 40tb of scratch space laying around in order to re-do that raid (your exact point about storage spaces, but it applys to any big bundling of storage including raid).
in addition, most raids can't just be (easily or simply) modified in place*. so i can't just add one drive to the raid, nor can i just pull a drive and shrink things.
basically raid (or any type of lumping of the storage into one big pile) makes everything harder and take longer and more complicated.
this, combined with some of the limitations of raid (see the video i linked), i usually don't bother with raid except for tertiary backup storage and there, i use something (zfs/truenas) that lets me manage that space better, as well as provides higher protections, and even then, i think if it was practical for my situation, i might not even do it there.
in any case, ymmv
* Unraid perhaps being a bit of an exception although