Personally wouldn't use an elliptical stylus for CD-4. My preference would be simply an Audio Technica w/Shibata for the simplest most trouble free setup. Quad D's AT recommendation is a sound one.
Not sure if these explain everything, since I've only skimmed them. We had a 3D display at Pacific Stereo (CBS inc.) provided by AT. It had a crystal model of each stylus type, 4" tall, and circumference like a thick permanent marker.
We were AT's largest dealer, with 110 stores. AT's Precept line was created for us. We had exclusives in our regions. You couldn't buy it anywhere else in Chicago.
Carried all the cartridge brands, incl several audiophile lines. We sold ADC, Shure, Empire, Pickering, Stanton, Dynavector, Ortofon, Grado, AT, Ortofon, Micro Acoustics and more. May have forgot a couple...
I use a conical for old 78's
AT & Ortofon Shibatas or fine line for all else.
Elliptical is oval.
I would be sure to buy something with a nude diamond. Most cartridges use bonded. That is a metal shank attached to the cantilever and a diamond tip glued to it. Glue fails, and you've got a blunted hunk of metal playing LP's. Nude diamond is one piece mounted directly to the cantilever.
Shibata, fineline (or microline, etc.) are modified oval. They are mostly the same, EXCEPT a Shibata has a "squared off" back end, fineline is rounded. Slightly less record wear on fineline and no "squared off" back end, which could break if it gets severely worn. Shibata was designed to do less record wear than elliptical and trace the groove better w/less damage to the carrier signal.
Found some good info & explanations at Crutchfield:
How to choose the right one for your turntable
Welcome to 'Question of The Week! This week our Audio Solutions Team discusses the different types of styli for turntables."