the absolute lossless way of exporting a graph is to save the plot as a vector graph. And then use insert picture from device in word to insert the vector graph is clear enough for me.
e.g.:
library(tidyverse)
mtcars %>% ggplot(aes(x = mpg)) +geom_point(aes(y = disp)) +geom_smooth(aes(y = disp))
ggsave("./plot.svg")