What is specific to New Jersey
New Jersey has no state-specific Medigap enrollment rules beyond the federal ones, so your six-month Medigap open enrollment window is the one that matters most here.
What is the same everywhere
The enrollment calendar is federal, so it does not change when you cross a state line. Your is the seven months around your 65th birthday. The runs October 15 through December 7 every year. A opens only when a qualifying life event — such as losing employer coverage or moving out of a plan’s service area — gives you one.
Late enrollment penalties are federal too. Going without builds a penalty that is permanent once it starts, and delaying without active employer coverage does the same thing to your monthly premium for life.
What actually varies
Which plans exist for you is decided at the county level, not the state level. Two towns thirty minutes apart in New Jersey can have meaningfully different sets of options, different networks, and different drug lists. That is why the first question I ask is your ZIP code, and the second is your list of doctors and prescriptions.
I do not publish plan lists on this site. They change every contract year, and a stale list is worse than no list. If you want to know what is available where you live, ask me and I will pull it up with you — or check every option yourself at medicare.gov.