Assuming your Galaxy S18 reference is just a typo, if you're actually thinking of something like a Galaxy S8 that is a better option than your daily usage Z Fold. I'd suggest you avoid one of those one-button rooting apps like Kingo and instead opt for a process like TWRP/Magisk:
XDA has helped me with many previous projects, its about time I gave back to this community. I have been trying to fix my Samsung S8+ which took 3 to 4 guides from this forum and combining into one. From what I can tell, pre-2019 was a lot...
forum.xda-developers.com
It's only a bit more involved but results in a cleaner, less obtrusive quasi-root. Since you're apparently willing to educate yourself on the rooting process, getting comfortable using the Odin utility will give you better sense about your phone's internal functionality.
You might also want to be sure you download and save the appropriate Samsung stock ROM for that particular model of S8 (or for whichever phone you intend to buy for this project). Just in case a problem occurs while rooting the phone or later after you do root it, having a stock ROM on hand allows you to flash the stock ROM to restore the phone into fully functional condition again. (.... and then root it again to start over).