Serial Data for PIC16LF84A

[skimask]

I am only transmitting 4 bits from the transmitter to the receiver. Would manchester encoding be necessary, because from what I read it's not needed.

Then you didn't read enough of the posts.
Generally speaking, you can't send straight serial data into the transmitter and get that same straight serial data out of the receiver.
As all of those posts said, you have to sync up the receiver by sending sync bytes.
Since you are only sending 4 bits, you encode them at the transmitter end (giving you 8 bits total), and decode that byte at the receiver end (getting back your 4 bits from 8).
But again, as I've stated elsewhere, you're dropping all the way into your project without taking little steps first.
Hook up a couple of LEDs to the RX PIC and get those to flash on command from the TX PIC, anything to prove that you can write the code needed to do the job.
Then work your way up to sending functional data across the RF link to do the job you need.

As to whether or not manchester encoding would be needed?
Maybe not, but your data will be a whole heck of lot more reliable (up to the point of being almost completely unreliable if you didn't encode it) at the receiver end if you implented some sort of coding.

come to think of it, do a search on 'data slicer', will probably give you a bit more info.