TBH I wouldn't bother buying new transceivers of unknown brand/origin on amazon or ebay. I also have a collection of such transceivers somewhere in a drawer at home, but as they tend to be somewhat picky with one vendor or another (usually intel NICs) I replaced them all with something I *know* works and doesn't let a 'quick upgrade' in the evening become a night-long troubleshooting session...
So I'd just go with FS.com - they deliver really fast, are cheap, have a proper 'no BS'-warranty and their transceivers 'just work'™
At work we use them everywhere in intel or Mellanox NICs as well as cisco switches and never had any issues.
I once had a transceiver that died maybe due to overheating (passively cooled appliance...) and received a replacement the next day without them asking any further questions.
They also have amazingly good and fast support, so if you are unsure on what kind of cabling you might need or what you should use in a new deployment, they are always helpful in recommending some options.
(no, I'm not in any way affiliated to FS, just a very statisfied customer for 10+ years)
If you use cisco switches you can set the (undocumented)
no errdisable detect cause gbic-invalid and service unsupported-transceiver options, so you only have to order the transceivers for the NICs you use; the switches will take them regardless if they were programmed for e.g. intel or mellanox.
If this is just a local cabling (i.e. home network) that will never need to e.g. expand to multiple buildings, I'd just go for the cheapest option: multimode transceivers and OM3/4 cabling.
If you also have cabling that runs over more than 100m and has to scale up to or beyond 100Gbit one day, I'd go for singlemode cabling on those longer runs or those that are hard/tedious to replace later. You can then use the 'dual mode' 1310nm transceivers for 10Gbit that can be used with multi- and singlemode (
https://www.fs.com/products/11556.html).
This way you can use multimode cabling at the rack and singlemode for anything that leaves the rack/building but still use the same transceivers for both. I discovered those "dual mode" transceviers way too late, but am using them anywhere now and it made life SO much easier.
For >10Gbit within the rack just stay with multimode as the transceivers are (a lot) cheaper; only for the long runs one has to go for the more expensive singlemode transceivers. FS also has those "dual mode" transceivers for >10Gbit, so depending on use case this could be an option too. I have all the >10Gbit links only within the rack - everything that leaves the rack is just distribution network that won't need higher than 10Gbit links for quite a while, so I just used normal MM transceivers for >10Gbit.
