Stripe 2 will improve performance, FTT2 will lower back end write IOPS (possibly an issue, possibly not depending on back pressure and cache fill). In theory it could improve read cache miss performance, but between ARC, the read ahead caching system for cache misses and everything else I wouldn't expect much.
Smaller disk groups, more flash etc. I'd recommend you fire up VSAN observer and look at your Read Cache hit rate and see if another disk groups (and more flash) would be a good idea. You tend to get diminishing returns trying to push it past 90% cache hit rate
So keep in mind that unless you have a really bad object balance issue (It would require a lot of effort to be honest, of careful VM creation and deletion and then setting SPBM policies to create it) you should see a heavy many to many rebuild (IE when a disk or Disk group is lost the mirror pairs for those objects will be scattered across the cluster, and they will rebuild into the free space of all other disks until the mirroring policy is re-enforced). Keep in mind that objects is already chunked into new components ever 256GB (by default). Because of this design as the cluster gets larger and ads more failure domains (hosts, disk groups, drives) you should actually expect rebuild performance to get better!
Did you experience performance issues on your rebuild, and if so what are your flash/disk types and make model of your server HBA etc?