In making a technomancer it is clear that a technomancer can not have all CFs. In the BBB that TMs can feel the signals and data flow around them, would that imply that they already have scan/sniff or would I need to thread up scan/sniff to do the basic things technomancers can do?

BTW, the wording is confuses me, what is the difference between scan and sniff? (The way I read it scan sounds like a special case sniff)

One is for wireless traffic (mostly when you are NOTin a host), the other for wired traffic (when you are in a host)

One thing to note is that Scan is only needed when you are searching for hidden signals. For any commlink in active or passive mode, you can just do a Matrix perception test in either AR or VR see all the signals in your area.
Sniffer is so you can intercept the dataflow and 'listen in'. Example would be listening in on the conversation between a rigger and a drone or one of your buddies and his fixer. Most of the time, you will have to decrypt the dataflow before you can listen in.