Down size logo

I have logos in different formats such as png jpg eps pdf svg (let me know what format is right and I’ll send). I need them to be trimmed and downsized (I think) to be used on my website. I need help in determining what format to work with and that you ensure the image quality is good and yet not to heavy to load (seo purpose).
It is 4 versions of the logo and I need them in 4 different sizes so I can choose later.