Replacing HDD of Fusion Drive with an SSD

Hello I know this question maybe asked a lot. So I have my iMac late 2013 that i want to upgrade from Fusion (128 blade/1TB) and I just got all the neccesary parts. Samsung ssd Evo 1tb.thermal sensor the works anyway. I want to basically just get rid of the spinning HDD and toss in an SSD to replace it. I know the imac comes with a blade SSD and is fused with the hard drive. Now what I'm planning on doing is using the blade ssd part as boot up drive along with my main Video and Audio Production editing software so they utilize the PCI E speeds and I guess the Sata SSD for the rest of the files like actual videos and audio files. Now from. What I'm understanding I would first need to split the fusion drive to replace the HDD with the new sata SSD and go from there. Sooo. My question is best way to make sure everything is backed up as I'm not sure what and where has been stored on the current fusion drive like what was stored on the blade part and what on the HDD so getting a full backup is like normal? How should I go about doing all this. Ps I'm currently on Catalina OSx

1.Best way to make sure all is backed up

1. Splitting the drive
2. Maybe I can setup the Sata SSD externally first before cracking the imac physically open to install it all so when I do do it it's ready to go
3. Install the OS on the blade ssd and the Apps

I assume I'll have to reinstall these apps manually now that the drive is split like my Logic Pro X premiere pro etc and hopefully I can just route the plug in folder to the Sata drive

I know this may seem like a lot of random thoughts because as I'm writing this I'm thinking out loud. Bottom line is it even worth the headache doing this to upgrade the HDD to SSD or is it not such a significant upgrade that I should maybe skip it and return the drive or use it externally which I rather not. I hate more and more Usbs I like internal baby (that's what she said) sorry. I may have more questions once someone gives me some tips I've read a bunch of information but feels like the more I go down the rabbit hole of information. I appreciate all and any help possible thanks in advance