Hi .. I don't have the exact same scanner but I have the Epson V33 that is an older model of photo scanner.
If your sketches are small the 600 dpi resolution is more than enough for the prints you want to do.
.tiff files are uncompressed but they are not that convenient if you want to edit something especially if your pc has not enough processing power. Average pcs don't have that powerful processors neither that much RAM to edit very large .tiff files in multiple parts. ( but if you have a very good pc go for it).
Regarding the sizes and the compression.
Don't post on the web very large images in the higher resolution unless you are sure about the website that you upload them. I assume that you don't want to see your sketches in made in China prints!
A decent size for uploading images on your website is 800px on their larger side ( that gives a printed image of about 9 cm ( in its larger size) with lower resolution.
The best file type is .jpg with decreased resolution.
Don't post .tiff and .png online, they can be edited easier than . jpg, because the .tiff are uncompressed, and the .png are slightly compressed but still can be edited. For FAA post .jpg in high resolution and size. The smaller the size the smaller will be the file as .jpg can be compressed and you can lower their resolution if you want too. Once you do this and you save your image file on whatever resolution you choose they can't be brought back to something better. That is the reason why you ought to keep the original scan in full resolution and upload on the web the lower resolution, smaller size copies of the original image or the full resolution .jpgs for FAA.
If your intention is to present your images on your own website don't forget to add a watermark with the sing of © and your name or your website.