The_Reason_is_Me

I am building a video storage server at home, but I have ran into a problem in my plans. My original plan was to use TrueNAS Scale with ZFS and start with a mirrored vdev of two 18TB drives. I then wanted to expand it one 18TB drive at a time into a Z1 vdev of about 5 drives. However I found out from online research that it is not possible to just convert mirror vdev to a Z1 or even expand a Z1 vdev. Does a software raid solution exist where it is possible to start with just two drives, add other drives later and still keep the n+1 topology? This is the minimum I need, however the possibility to add an extra parrity drive would also be amazing. Let's say once I get to 5 drives (4+1) I could add an extra parrity drive to get 4+2. Is this somehow possible? If so what solution should I look into?

I am moving all of my gear into a rack and building a NAS and I would like to be able to connect this NAS to a SFP+ port on my switch. I will be routing every other network cable thru a Patch panel and all the positions in my rack will be filed up so I really don't have a choice. I was however unable to find a SFP+ keystone. I can either just pull the cable thru an empty hole in the patch panel, or use an optical cable, but I wanted to know if a SFP+ keystone even exists and if I could use them.