EasyPopulate does not influence the size of images. All it does is load the FILENAME of the image, and its sub-directory location on the server (if needed). So if you have an image called "my-special-product.jpg", then that is the text string that gets parsed (stripped into) the resultant HTML page... which then re-calls that image and places it wherever it is located, onto the browser screen.
Other settings (including the original size of the image) will determine what and how it displays. Most of the settings for image sizes are in the Admin Panel, under the CONFIGURATION menu.
I generally size my main product image to the same as the admin settings - so my product images are ALL square, and are ALL 600px X 600px. I tend to compress them down as far as possible, and use a professional image editor (Photoshop) to do this. Cheap 'n Nasty image editors (lots of freeware ones on the web) just don't cut it if you want good compression, but also retain a top quality image.
I also use Image-Handler, which has an array of useful image management tools.
On the use of "Social Network" sideboxes and such like... I avoid them as much as possible. They are a distraction, and if your objective is to SELL STUFF, then you don't really want links that take your customers away from the store.
The sole purpose of a webshop is to get people to add stuff to the cart (as much as possible) and then to checkout and pay.
If they want to natter and gossip, then let them do so AFTER they have parted with cash.
I see social network sites (indeed all other elements of my organisation's Wide Web Presence) as a means of HARVESTING potential customers, and then guiding them to the webshop.
Once they are in the webshop, my key aim is to get them to leave the site through ONE PLACE ONLY - the CHECKOUT-SUCCESS page.
If they are given reason to leave through any other link, there's only a 20% chance they will return to complete a purchase.
Out-bound links on a webshop are like saying to your customer... "Bored? Why not leave this shop and go to the bar across the road where you can gossip and natter to your heart's content..."
Keep the customer's focus on making purchases... nothing else matters. Use your wider web presence to trawl them in, and then use links on these other sites to point to your products, your offers, and info that gives people a very good reason why they should be giving you a share of their wallet.
