Do you have to use Cox Panoramic modem or can you use your own 3rd Party modem?

You can use your own.

Cox compatible modems

Scroll down and pick one. I like plain modems without routing or wifi capability. They tend to last longer in my experience and I like to choose my own router.

I have cox and my wifi sucks and recommendations for modem and router?

I don't think the modem matters so much as long as it's DOCSIS 3.1, and I avoid combo units like the plague for many reasons.

Router and wifi, the easiest will be to get a mesh system. I guess any of them is fine so long as you don't need to do anything fancy.

Personally I like ceiling-mounted wifi access points because I can place them exactly where I want with no cords showing and no shelf or counter space taken up. For example I have one in a hallway which covers 4 bedrooms, it had to go on the ceiling and it's not even noticeable. Very clean. Of course it does take more time and you have to be handy or willing to pay someone to install.

That's the same one I use. Could not remember the model name. Have that paired with Google wifi. For TV cox gave me newer contour boxes with cloud DVR. I could not get them to work with my setup. Something with the mesh system or something was not compatible. Had to go back and get older contour box with an HD which I prefer anyways.

I have an extra surfboard. Think it's good for up to 300MB speed.