.177 pellets will be just fine for 50 yards, if things play ball as they should you will be making 1 hole in the paper, maybe one that slowly grown in size and get a little ragged, once you reach 1/2 - 3/4 " hole size it should stop growing in size.
With moderate power and a moderator the loudest thing will still be when the pellets land in / on what ever pellet trap you get / make.
But high power will not be much louder, pellet trap can also be a lot less loud than the generic steel pellet trap which will be "loud", so people mention rubber mulch for instance, that will be nice and quiet compared to just having a thick board or even a slab of concrete as a back stop.
A berm of sand are also pretty quiet in catching pellets and slugs, you just have to take a shovel to it now and then as it collapse as you shoot into it,,, well at least if it is a small berm up against some boards, 5 - 6 cubic feet i think will do it for a nice little sand backstop.
A .177 shooting 13 and up grain pellets or slugs, well a regular thickness fence board, it will make holes in, even if you go to a lot thicker piece of wood, well shooting the same place again and again and you soon drill a hole thru that too.
If you want to and your rifle can, you can change to slugs and push it out to 100 yards. i personally shoot ( slugs ) 75 M with my .177 and 100 or more M when i feel for that once in a while.
You can also up the power if the rifle allow for that, pout in a 16 grain pellet like the JSB Beast, and you will be able to drop fairly big things just fine.
10 . 13 grain are about the middle weights, though 13 grain are called heavy, the lightest stuff are around 7 grain, personally i favor 13 grain in pellets and slugs which i mainly shoot.
The heavy 10.34 grain and 13.43 grain monster redesigns, they will also fairly accurate ( no wind ) shoot longer distances. At least if the rifle are good, the shooter are good, and the setup too, you can dial a adjustable rifle to a place where you can barely hit a barn door, and opposite tweak a little and maybe gain 1/2 - 1" in accuracy.
The heaviest slugs are 20 grain in .177 caliber, shoot them at high speed ( 1000 FPS ) and you are up around 50 food pounds, which is more than my 2012 .22 FX Cyclone rifle will do with the 15 - 18 grain i mainly shoot with that one.
If the wind are not bad, i have no problem keeping 95% of my shots on a 2" shoot and see splatter target, and i will take shots at flies that land on the target too, and thats at 75M / 80 yards or so, or longer distances ( 100 yards = 91 Meters as i recall )
If your rifle are not adjustable, well get a tin of every relevant pellet, and you will soon find out what pellets your rifle like, and what ones it absolutely DO NOT like, thats the old fashioned adjusting for accuracy,,,,, finding that one good pellet, and then just shoot those and be happy.