Can I replace Fusion Drive with ssd

so I just bought 2019 27" iMac with 3 ghz 8 core i7 cpu, 16gb ram, 570x 4g vga that is 1tb FD with 28gb(could be 32gb, wrote it 28g cuz thats what system info says) of nvme ssd doing boot ups and cache works with 1tb hdd storing datas.

I'm here to replace it with my 1tb nvme ssd and 2.5" sata ssd which is gonna be pulled out from my previous late 2015 27" imac that contains all the datas stored from my previous machine. red about Fusion Drive being little hassle that it needs to un-fused to get it used right but can't seem to find out any info regarding to that, had to be sure before popping up each of the screen lid for a replacement.

and also, the fresh 1tb hdd that will get pulled off from my 2019 iMac is having plan to be placed at 2015 iMac which was not a fusion drived iMac. my theory on it tells me its fine to do so but would like to be sure on it too. I'll prolly pre-install os Monterey on 2019's 1tb hdd then do the replacements vice versa.

if I'm having to some how un-fuse the Fusion Drive option in 2019 iMac, please let me know how can I approach doing it so. thx!