First, yoga is really good for all of this, and there are a lot of different styles of yoga out there -- so your class experience is going to vary. Even within a given style of yoga, teachers approach things differently, which means you're going to have a different experience.
Second, you don't need to "impress" anybody. As a yoga teacher, my see my job as teaching the student how to get into the proper alignment of the posture for their body, to get the most benefit from the pose. Having worked with people with only one arm, full hip replacements, and all manner of lack of mobility (whether from sports, general life, or age, or what have you), I can tell you that no one person looks the same as another, and trying to makes you look more foolish than just following the instructions.
If the teacher is good, s/he is looking for you to get to the best and most beneficial modification to you, and trying to go beyond that or look like someone else is *less impressive* than working diligently to do the posture right in order to get the benefits.
It would be the same if you went to the physio who gave you a specific movement to heal your shoulder (for example), but instead of doing the movement as shown, you went online and found a "full version!" of the movement from a really healthy, flexible person with the full range of motion there, and then "pushed" yourself to "look" like that. Hint: you do not look like that, for one, and for another thing, you are further injuring yourself.
The real "trick" of yoga is backing off and working toward finding the right position from you, and then developing your mobility from that point.
And anyone who knows anything about yoga would be *seriously* impressed with someone working to achieve *that*.
Third, sweating -- particularly for men and particularly in the beginning -- is really normal. According to the "legends" so to speak, you are "burning off impurities" but that I really think it is 'putting in more effort up front because you don't know the movement.'
Basically, you are inefficient. You don't know the moves, and you are trying really hard to get it right. IN addition, yoga is more vigorous than people expect, so they go in with the idea that it's easy, and it turns out that it's not (and it never gets easy, that's kind of the point). You don't know anything and you also dont' know how to regulate your breathing with this movement modality as you might with others. As such, you put out a lot of energy and sweat like a man-man.
It also supposedly really stirs up the "internal fire" or heat (in fact, over time, you learn to do this and not do this with the breath), and so that's another reason why you are sweating.
It's no big deal. And in general, men often sweat more in yoga than women just as they sweat more than women in general (even just standing there).
And, it'll decrease as you become more efficient in the movements (once you learn them, learn the modifications, and how to breathe while doing them).
Next, yoga just does good things. I'll give an example about "being in good shape."
For several years, the only movement that I did was walking and yoga (that's what I'm currently doing, even). My husband and his friend did hiking, running, and weight lifting. We were prepping for a big hiking/camping trip, where we would do 10-hr days on trails (then cushy camp in the evenings).
Over and over they kept telling me that I was going to die on these trails because I wasn't in as good shape as they were. They were running, hiking (or sport specific training), and doing their weight training! They were SUPERFIT!
So, we get to our first day. We wake up early and have a simple breakfast, then head out onto the trail. It was two miles in before heading up, and in the end, it was a 12 hr day (it was quite a difficult starter).
I was fine. my feet didn't hurt, even though I was wearing very thin tennis shoes rather than hiking or trail shoes. I had no loss of breath, no exhaustion in the legs during or after. I was a tiny bit sore the next day, but not big deal.
The boys, on the other hand, were wrecked. Feet were so sore, they had to take the next day off. Legs were super tired too. They wre winded for much of the hike.
Yoga trains you differently. I don't know why they were so "out of shape" --particularly since they were so sport specific. Maybe it was a mental game.
but Yoga seems to make it possible to adapt to a lot of things because the body is agile and you are used to working with your breath (and adjusting it) based on the shifting changes of the practice itself (sequencing of postures, the postures themselves as you progress into deeper versions and 'sister/cousin' postures, etc).
So, even though you are in decent shape for a lot of things, yoga -- like rock climbing and several other things -- are really difficult on a body that doesn't have the mobility training and is trying to figure out the new movement. It's just difficult.
For me, learning rock climbing was hard physically because it was new movement, but the breathing was fine because it was a lot like yoga.
Finally, yoga only works if you do it consistently. You'll get more benefits the more you practice -- and most people find that twice a week is good for progress, but it is slow progress. When you get to 3-4 times a week, the progress is faster. More than 4 times, and it speeds up again.
You don't have to take class every time you practice -- there are lots of sequences that you can tack on to the end of your normal workout for example -- but it's good to practice frequently to get faster results.
Even so, just being CONSISTENT is most important, so one class per week is a good place to start.
1. at this point, just shop around for classes and see what you like. go to every studio, gym, whatever that you can find and see what 'resonates' with you in terms of the style/culture/etc.
2. focus on what you can do -- remember, this is to develop your mobility, and that's what impresses people in yoga class (though honestly, why do you need to impress anyone?). So, it's meant to serve you, make it serve you. Focus on alignment and doing it right rather than attempting to "look" right (because I guarantee you, if you are trying to look right, you are doing it wrong, and then you get zero benefits and might even injure yourself).
3. practice consistently -- at least once a week, more if you can.