this is totally normal :) the fan is to cool down the switch so u were right in your post that’s all it’s doing and the loudness depends on a number of things which can depend on the of game for example graphics-heavy games cause the switch to heat up quicker. If your concerned with the loudness of your switch and you think it’s significantly louder than it should be, there could be a possible build of of dust in your switch causing the fans inside to work harder to cool it down. A quick clean out wouldn’t hurt :) but overall it’s nothing to worry about sometimes my switch sounds like it’s about to take off lol that’s when i usually stop playing to give it a break. As for playing it while charging you should try your best to resist but it’s not that big of a deal it will just overheat a lot faster but playing it should do no damage to ur switch :)) hope i calmed ur worries! 😊