Dumb noob question, sorry

Ok, thanks! I was playing a map and was able to jump to get a key and for some reason I didn't think I was supposed to. Good to know!

I always play as if jumping is disabled unless the mapper says otherwise or it becomes clear by playing the map that it's required. I rarely play anything outside limit removing, boom or mbf but back when I played more gzdoom stuff this approach worked well for me. It's possible more mappers could be making stuff built around jumping now but at least from my past experience it was always fairly uncommon.

EDIT: Saw that you've been playing some of the DBPs judging by your posts. Since they are made for limit removing ports they are built for the limitation of no jumping. So part of your answer is that you can make inferences depending on the maps format. For example if specified as vanilla, limit removing or boom you can infer that they are made for no jumping and will be correct 99.9% of the time. If you're new to Doom it takes a while to understand the different formats if you even choose to pay any attention to them though. 

I can say for sure that most testers for DBP will often test in a port that most closely resembles vanilla Doom with the default settings, as this is better for checking for map errors than GZDoom + all the personalized configurations one might have for it. GZDoom tends to overcorrect engine bugs that some level designers utilize as features.

However, I'm of the opinion that a wad that is well designed will still be fun even if you 'break' it with jumping.

GZDoom is kind of its own game entirely, as it pretty much rewrites most of Doom's code from scratch to correct for errors and oversights in the original executable for the most solid, bug-free experience. But if people play with this source port, maybe with gameplay mods as well, this should be a valid source port to test with.

If someone were to test a DBP map and say "I can easily jump over this" it's probably best to consider that a valid criticism than to dismiss it as a negligible zdoomism. Players will always play in their preferred source port. I say this as someone who has not received much direct testing feedback from players that test in GZDoom with jumping turned on, so my maps tend to have a lot of oversights like this.

Compatibility levels are for the different formats I mentioned and for different engine behaviors between the commercial games. If you've been playing Quake mods for some time you can sort of think of it as some of that games mods, particularly older ones having compatibility issues with different source ports depending on which one they were made for. With Doom many source ports try to accommodate for that by basically forcing certain engine behaviors with comp levels. The gzdoom settings are fairly inaccurate though as it's almost an entirely different engine at this point so it may break things that aren't an issue in more accurate source ports and vice versa. Also things that worked fine in older releases of gzdoom may not work properly in newer releases because of this. That's a bit of an aside though. As a casual player you can throw most things at gzdoom and not run into too many serious issues. It's generally good practice to check the readme before playing to see what source port it was tested in though. It's a little more involved than playing quake mods just because of the number of different source ports and behaviors they have. 

They are not linked to jumping though. That is a separate option in most source ports so a mapper could make a map in any format that still requires jumping if they want but that is fairly uncommon from my experience. So basically it can just give some insight into the mappers intent. If you find a map that is explicitly stating the use of certain formats or a comp level (-cl) then you can fairly safely assume that jumping was probably not intended. If it was the mapper will almost always make it very clear in either their readme or forum post (outside of the occasional new mapper). In the end though the overwhelming majority of maps out there are made without jumping in mind so ignoring it as a feature entirely unless it pops up as a necessity is honestly the simplest way to deal with it imo.

As for ports I use DSDA-Doom almost exclusively and gzdoom only when absolutely necessary. I don't like the inaccurate feel or the bells and whistles of gzdoom, among other things. That entirely comes down to personal preference though. What you'll want to use depends on what and how you want to play. Tons of options.
The video here may be of some help: 🌟 A Subjective Look at Doom Source Ports in 2024

Yeah, it will probably just take some time to get used to the different ports and what they do. In Quake, I've moved through a few different ones until finally understanding their different uses and settled on the one I prefer.

I found a launcher called Doomrunner that I use and it's working pretty well so far. For Quake I used QS, then Ironwail for a while but switched to vkQuake because it supports particle/smoke effects and makes Arcane Dimensions maps look beautiful. A new version of vkQuake was just released like 2/3 weeks ago, too.