BD1, the 15-22 is such a neat handeling and pointing package as it is, if you start loading it with stuff you will never use it will gain weight....fast! A light rifle is often a great deal more fun unless of course your desire is to build a bench rifle where weight is not a negative. One good thing about the AR platform it easily is built up or changed along with your desires. Welcome to the forum, there is a wealth of info here just ask.
I've got a Spikes Car1. It doesn't affect accuracy at all.
The added weight is a good thing IMO. The 15-22 is too light. When you're used to transitioning from target to target with heavier(normal) rifles, it's easy to overshoot with a lightweight one.
It won't affect accuracy and is personal preference so depends if you like the look or not. I prefer to keep it light but if I were to add one it would be a full length (6"), that recesses into the handguard.
Take a look at tacticool22 and kineti-tech.
Have a look at the picture thread and also research how to correctly remove the flash hider / birdcage without damaging your upper.
Add one for looks. Mine is very light weight and has an open back to comply with some screwy ATF rules. If both ends are closed and there is a chamber between them, they say you have a suppressor on your rifle.
Sometimes the crush washer helps, sometimes it does not.
If you put fingernail polish on the threads, use no more than a drop. And a small drop at that.
By the way... the reason I said don't use Loctite is because unlike a flash suppressor on the end of the barrel, once that shroud is over the barrel there is no place to hold onto the barrel with a barrel vice to get the shroud off. And of course there is no way to remove the barrel until the shroud is off.