Realunlucky and others covered your question well! If you are just trying out elk hunting it may not be worth the investment of an expensive pack/frame. You may want to try a pack/bag off Craigslist, Ebay, or the classified section on this website to give it a try. I used an abused a large volume Arcteryx Bora 95 internal frame pack successfully for years. You can likely pick up a nearly new one for around $100.
If you are serious about elk hunting you'll find that is definitely worth the investment for a pack/frame capable of 100+ lb loads. If you want the very best you may want to look at Kifaru or Stone Glacier. Although my Arcteryx functioned well, I've benefited by a lighter pack that is slightly more comfortable. I went with Kifaru several years ago and have been happy ever since. Kifaru offers a bunch of bag, pocket, lid, and accessory options. Unfortunately Stone Glacier didn't come in camo which was the deal breaker for me. You may want to look at the overall weight and volume of packs before making a decision.
If it were me I would buy an oversized bag. You'll have plenty of room for gear plus an elk quarter. My preference is a bag that is capable of at least 6,000 cu in of gear volume and some sort of internal frame for 100+ lb loads. All you need to do is cinch down the bag tight with small loads and you're still ready to comfortably pack out a large elk hind quarter your first load. Most smaller packs with no frame or small bags are generally designed for low volume and 50 lb or less loads. They will be torture on your back, neck, and legs on steep, uneven terrain since they aren't designed for hefty bulk/weight. I started off elk hunting with an old school Cabelas guide bag and frame. It worked but was actually fairly dangerous. The last time I used it I was hauling out a bull hind quarter. The load shifted (pack frame went side-ways) when I was climbing over some rocks and I ended up-side-down like a spun over turtle! I learned my lesson that a frame that is 2 to 6" from your back isn't stable on sidehills and it's impossible to haul the load close to your center of gravity (your back). The load is constantly trying to shift away from your body while on sidehills and uneven terrain. All this twisting and turning is torcher!
The modern day internal frames are built with that in mind. The better packs have load lifters, padded straps and belts, quick drying and ultralight/ultra-tough materials that withstand use and abuse. Their frames generally fit like a glove to your particular body frame size. With that said it is well worth the investment if you plan on hunting a lot!