The sales brochure for the year you are interested in will spell out the differences. According to the '18 sales brochure, the SR5 Premium adds (over the SR5):
-Color keyed bumpers
-Premium Audio w/Entune app suite & integrated navigation
-Softex seats instead of cloth
-Homelink (garage door opener)
-120 Volt receptacle in the cargo area
-Auto dimming mirror
The Limited adds:
-Auto head lights
-Chrome inserts on the bumpers, chrome door handles, etc
-Touch sensor lock/unlock
-Moon roof
-20" wheels/tires
-Dual zone climate control
-Heated/ventilated seats
-Smart key system (push button start)
There are several options that are available only on the Limited, for example automatic running boards.
Going through the matrix, I could have missed something, so please don't tar and feather me if I have.