I don't know what color your plaid pants are, as long as they are not horizontal.
In fact, it's not that plaid pants will be fat, but that too many colors will be more conspicuous.
Will turn their attention to their pants.
Generally speaking, plain plaid looks good if it is well matched with coat.
Just wear a monochrome coat, not too complicated.
Have a nice winter ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
Blessings ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~