Display one or more customer/client reviews in multiple columns and rows, or a slider. The reviews can be boxed or simple. You can set the rating from 0 to 5 in steps of half-star, add the photo of the author and a small company logo.
Page speed impact:
Low, unless you add large unoptimized images. Make sure to optimize your images with TinyPNG before uploading. Use optimized SVG files whenever possible. It may be slower with the slider enabled.