We are using NFS for our own stuff. This is well documented and works. I never tried Gluster. If we host at customer sites we are using their infrastructure network mounts (which can be anything, including VMware, containers). On Amazon, EFS is what they provide with an NFS4.1 protocol.
With RelStorage one does not want to store blobs in the DB (except with Oracle they say it's not a problem, I have never tried this). Thus, you need a storage server anyway.
My measurements regarding ZEO blob transfer versus shared blobs with NFS are about 5 years old and I can not find my protocol from this time. But on load, the blobs slowed down the Zeo connection significantly. These days, there is a newer ZEO in latest Plone 5.1 and this might change all this. We need new measurements.
The second disadvantage is, the local blob disk cache needs plenty of space. So every (virtual-) machine (or container) needs a large cache for blobs. This may be downsized but at cost of speed. If this is no problem in your infrastructure, that is fine. Here it was often - also on customer hosting centers - a problem. Most of them outsource their infrastructure, so they pay for all disc space.
If you want to get all binary load away from Plone/Zope and ZEO there is also collective.xendfile. We developed/ used it successfully for some Plone 4.3 sites with large blobs. It utilizes web server capability to turn a backend response header into a file delivery. I suppose it needs some update to work with Plone 5, thus saif I never tried it.