Looking at Africa, where does an inland sea (with a giant island) stop and three continents begin?
Pretty much if the tectonic plate that is the majority of Africa splits.
I’ve seen that same article; the projections are based off the tectonic plates buckling due to a civilization-ender asteroid that shifts the planetary axis by, I wanna say, 9 degrees. It also mentioned that this would put Antartica far enough from the pole that it would begin to dethaw and be the major reason for increased sea levels.
Personally, I have two go-to sources for planetary maps.
First are future guesses about Earth’s continental drift (I’m particularly fond of one from c. 225 million years from now, about 25 million years before the predicted Pangea Ultima... so there’s still a few gaps between the continents).
My personal favorite though is Weather Radar. Find a weather front with rain and screenshot it. The ground is your ocean and lakes, the storm radar image is the land with the intensity coloring indicating elevation (red is the mountain peaks, yellow lower mountains/hilly regions, green is plains/lowlands).
It’s especially good for sci-fi campaigns where you might be visiting a new world every few sessions because weather patterns are plentiful and just an couple of hours can be the equivalent of millions of years of continental drift in laying out a map.
Not really good for making entire worlds, but when I’m designing just a campaign region (most fantasy campaigns can get by with a 200x200 mile or less area), my default is to just find an interesting place in the real world, change the orientation and maybe do a mirror flip on the landmass, then drop some new vegetation (because I’ll often change the climate) and new cities/towns/villages onto it.
This ensures my river flows and elevations are always realistic and if you just follow a few quick guidelines on weather patterns and where communities form you can quickly bang out a very realistic regional fantasy map.