You can use 64k if you like. there is very little performance difference.

The problem is also fixed soon, in Ventura. (for when you eventually upgrade your computer to an ARM computer)

Questions: I don't want to get a kernel panic when updating from 6.2.1 to 6.3.

Q1. I don't need or use a Windows Boot, Since I don't use windows, is there any advantage to 64k vs 16k?

Q2. Would a possible kernel panic only apply when the 64KB vs 16KB issue occurs on a boot drive? My boot is a single volume non RAID PCIe SSD.

Q3. "Warning, version 6.1 and earlier do not support a stripe unit of 64k on RAID 4 or 5". You must upgrade the driver on your mac to 6.2 or later or a kernel panic will occur. " Since I am already running SoftRaid 6.2.1 with no problems, is it safe to assume that I already have this 6.2 driver ... So ... All of my worry about a kernel panic is a non-issue?

Thanks!

Here's my current build:

Mac Pro 5.1, 12 Core 347Ghz (2012 Cheese Grater) 

Mac OS 10.13.3 (High Sierra)

Boot Drive
is on a single PCIe SSD Non RAID

Bay 1
HD Boot Clone Back Ups, Non Raid

Bay 2-3-4
3X HGST 6TB HD Drives that are RAID5, and then partitioned into  2volumes.
16K stripe units 
SoftRaid 6.2.1

External Back Ups, Time Machine
3X HGST He8 HD In RAID 0
64k stripe units
SoftRaid 6.21