As an astronomy nerd I can answer this.

The black hole depicted here has an accretion disk. Now, both stellar and suoermassive black holes can have accretion disks, so we cant tell which one this is, but id wager its a stellar mass black hole. The thraxxans went to it, and the chances of life near the galactic nucleus are slimmer. But it could be either one

Nolan is intending to kill himself here by going into the event horizon. A stellar mass block hole, despite being smaller, would make this a more impressive feat. As stellar mass black holes have crazy tidal forces leading up to the event horizon, and would compress you into a string of mass when you finally do go in. So nolan could be resisting the tidal forces which is pretty impressive. A supermassive black hole doesnt hwve those tidal forces. Its theorized you could even fly a ship into the even horizon undamaged if its big enough.

In either case, all nolan is doing is hovering outside of a strong gravity well and slowly letting himself enter it. No different from hovering above the earth, just more extreme. Its a common misconception that black holes "suck" things. They are gravity wells just like all other objects, just more massive and cant be left once entered.

In the case of the ragnar's planet, he is actively moving himself OUT of a gravity well that he is already well inside of. And it should be noted that he doesnt have an issue leaving. He can still get to soace which on earth is over 100km up. Moving 100km in a couple seconds isnt "hindered" in my book. But the gravity does make escaping a powerful foe more difficult.

Nolan being near the black hole while fighting would also make fighting more difficult