Pinning max-links <2-4> comes into play when you do static pinning. i.e. the FETs (fabric extender transceivers or links between 2K and parent switch) are not in a port-channel.
For a 48 port FEX:
pinning max-links 1 : 1 group of 48 hosts to 1 FET links
pinning max-links 2 : 2 groups of 24 hosts to 2 FET links
pinning max-links 3 : 3 groups of 18 hosts to 3 FET links
pinning max-links 4 : 4 groups of 12 hosts to 4 FET links
So, all 48 ports will be associated with 1 FET if 1 uplink is used and max-links is 1. So subscription ratio will be 48 * 1 gbps per 10 gbps uplink : 48:10 = 4.8:1
For max-links 2, subscription: 24:20 = 1.2:1
So, to sum it up, a good practice is to use a port-channel for a FEX uplink. A better option depending on whether you have a 5K or a 7K is to use a vPC as an uplink.