I joke that doing these rides feels like I'm re-boring my arteries because my heart pumps so hard. I feel great afterward. Recommend!
You end up doing both.
I think I agree with you that these experiences are pivotal, because they are moments when you just are without thinking. That constant monologue some of us carrying our heads is gone, and the universe didn’t end.
Taking that information and finding the spot halfway between the two is the real lesson, IME.
Heck, a week ago I did a 100 mile MTB race, with the goal of finishing and being happy. While bits and pieces are there, some chatting with folks and things I saw along the trail, but I honestly do not remember most of the ~9 hours I was riding. It was just a thing I was doing, disconnected from most of the rest of the world, and content doing it.
(Note, I'm talking about XC/cross-country mountain biking, and to some extent trail biking. NOT the big downhill/jump/whatever stuff that comes up most often in media when sees mountain biking. It's still quite exciting, but far safer because it's really just riding bikes on hiking-ish trails.)
The community is pretty rad too, it has the atmosphere of surfing and hiking combined.
I also suggest XC / blue / "intermediate" / rolling trails. They're less exposed and dangerous than steep descents, and better cardio. The MTB industry and press is increasingly downhill-oriented, but you can ignore that noise. Before you buy a bike, try renting a few, and riding them on your own local trails. It'll give you a better idea of what sort of bike and riding you want. If you don't have much singletrack nearby but you have dirt roads, consider a gravel or "all-terrain" road bike instead (like a Kona Dew, Kona Rove, or Hudski Doggler). It's not mountain biking, but still a lot of fun, and you cover more ground. (They're also simpler and cheaper than modern mountain bikes.)
Bike fit is important, take your time to get it right. Don't buy the wrong frame size! (I've made that mistake at least twice.) Find a shop (or experienced friend) to help you dial in the fit, and expect to swap some parts. This (and physical conditioning) makes the difference between riding kind of hurting, and being comfy on the bike for 2+ hours.
Obviously you can get hurt. MTB injuries tend to be less severe than road cycling, because you aren't riding in car traffic. But several years ago I tore out my triceps, going over the front of the bike in a rock garden and landing on my elbow. That was a surgery and slow recovery. I'm fine now, and even with that injury, cycling has been a benefit to my health and enjoyment of life.
It can be a gear-intensive hobby. I have a mostly-bikes room. It can also be an expensive hobby (though doesn't need to be). Still much cheaper than motorcycles, sailing, and so forth.
Sorry, one last thing. Be courteous to hikers. Yield to them by default, call out if approaching them from behind. Making hikers feel safe and respected is more important than carrying your speed. When riders forget this, angry hikers show up to meetings and agitate for closing trails to bikes.
I am lucky enough to live within riding distance of a trail centre, they aren't the best trails but having any trails nearby in a suburban area is amazing. It's a 10 minute pedal and I get out once or twice a week to those trails.
They can be windy smooth trails through the forest, or rocky technical trails to test your bike handling, or gnarly steep downhill trails, or jump trails, the list goes on. You have full control over what you get yourself into, and I can just barely scratch the surface of the variety of riding available across all the disciplines and locations. The basics are the same, you and your bike on some trails.
You can develop your bike skills and challenge yourself on fast or technical trails, or you can just take it easy on flowy easy trails or cross country trails. You can dial up the adrenaline as much or as little as you want, and the terrain can be vary wildly from trail to trail so it's always new and interesting. You'll end up riding parts of your locale you'd never imagine and if you go travelling with it, there are trails in rainforests, deserts, mountain ranges, rolling hills, all over.
For the fitness side, you build strength and dexterity across your whole body as you ride more, and the ride up the hill will develop your cardio and often be interesting trails of their own.
Check out the Trailforks site/app to find trails near you, go rent a bike for ~$50 for the day from any MTB store. It's very easy to try without spending much.
The only equipment you need is a helmet, any bike helmet will do for your first rides. You'll figure out the rest of the gear as you go. Modern bikes are so easy to ride and have made it a crazy fun.
Another example - it's pretty damn hard to think about doing the laundry when you have 100+ kg on your back.
I have found my biggest mistakes were all when I had gotten comfortable with a weight and ended up losing mental focus. Thanfully no injuries. It seems I have to be nearing my edge to be forced into focus. I am better at opting in to focus now thanks to lifting I feel. Similar to downhill riding, all my crashes have been on easy stuff as I lost focus.
It probably helps that increased appetite never fazed me. I am hungry now, cool, I'm still not eating until dinner regardless of how I feel.
I’ve found Yoga and cycling to be the right fit, and they allow me to challenge myself without feeling too hyped up later.
But choosing to exacerbate that state when there are other options to achieve my fitness goals is counterproductive, and I’ve been advised to avoid it.
There’s an important difference between getting comfortable with hard things, and subjecting yourself to unnecessary/avoidable hyper-arousal states which can become their own form of health problem in the long run.
People injure themselves this way, and should pay attention to their bodies when exercising.
I also hate cardio but it is much more palatable if I'm on a mountain bike and climbing up for a descent trail.
That being said...
I really don't know any serious athletes who enjoy going to practices or going to the gym to workout. In my opinion it's rarely about enjoying the moment. Rather, it's about the way it makes a person feel when they're done. Or, it's about reaching a long-term goal and the joy that comes with accomplishing something currently out of reach.
And, of course, that type of joy can come from a wide variety of activities - exercise, coding, music, arts, etc.
Edit: Removed unnecessary quotes.