Chainguards , They do for me a primary job of stopping the chain from going past
the outer chainring on an upshift. I fit a chainminder on the inside ,
to catch any overshift on that side..
have a sturdy one , outside the 50t, on my Touring bike,
a 48t sawtooth looking thing, on my winter bike,
a 38t one on my Koga trekking bike ,
and a big one 53t on the Bike Friday,
and the Schlumpf Mountain drive came with
one for its 54t chainring..

+1 on tucking the trouser leg in your socks..
or folding and rolling up the trouser leg..

do it a lot, and you can sew on some snaps, velcro.. , Or get the leg tapered,
add a zipper .. I did that to a pair of Black charity shop pants.

My rain pants, since original topic was rain pants,
include a velcro strap arrangement at the cuff,
so no additional strap is needed.

though an additional one, with a reflective band on it
is an additional bit of 'see me' notice.