The only advantage a Variable power scope has is if you plan on shooting from in close to way out far. That fixed power SWFA 10x will do real good out to about 700 to 800. In fact, it will really do ok to about 1k if you are not necessarily trying to shoot tiny little groups, but instead are shooting at actual Targets (steel, deer, ect). For out at 1k I might prefer a 16x, IF I were trying for small groups.
My IOR 3x18x42 first gen scope @ 12x in the last 5 minutes of light or so will allow me to spot and engage a 1 gallon jug filled with red-dye water. Much beyond 14x in the same conditions and the scope starts to "Go Dark" on me. I mention this so you can scratch your head and go....OH I SEE... For many of us, hunting seems to really be about what, 30 minutes in the early morning, and 30 minutes in the late evening if you are lucky right?
Of course, for you it may be different. My IOR @ 18x on a average Day Time shot has plenty and then some for clarity. So, you kind of need to think what time of day / how much light will you have when you think of what power and what size objective you need. Exit pupil should generally be at least 3.5 for good clarity. You can calculate exit pupil by taking Objective Size (mine is 42) and dividing it by power setting (in my case 12 for late evening) which for me equals 3.5 Now this is something that any Really Knowledgeable Scope sales person can tell you. Call Nightforce and ask them, I am pretty sure they will tell you 3 to 3.5 If you called Scott @ Liberty Optics he will Definitely tell you the same. Again, just food for thought.
Now, the caveat here is QUALITY OPTICS...you can have a 24x scope with a 72mm objective and if the glass and coating are crap, then the clarity (Not Brightness!!!!!!) will be crap. You will see fuzzy navel crap, but really enlarged ...24x ;)
BTW, SWFA super sniper is considered to be good optics, and really solid hardware. Not high end, but Good! I would buy one if I were on a budget and needed a Good Scope I could count on.
Now as for 300wsm, yup it will work quite well for you! I have to say, the no reloading this hurts a lot...at $40+++++++ per box of 20...omg if you practice at all (going to have to to meet your goal) that thing will break you if you buy your ammo! Reloading CAN be both economical and easy, it is just that many of us get hooked after the fact and start to screw around endlessly.
Ok, so here is a suggestion for you. Buy yourself a Savage Precision Carbine in .223 and buy a **** Load of good ammo for that and practice, practice, practice, and Practice with it. Once you get GOOD with that, then move up to your 300wsm. Trust me, it will take a Few Thousand Rounds Down Range before your Real Deal Skill Levels come up to par where taking a 500 yard shot will be a "Good Idea". Especially if you do not reload, the purchase of that .223 will save you plenty of money. Another thing to consider is if you insist on just the 300wsm, you may very well burn the barrel out on it before you really get your skill up to snuff. Good luck burning out a .223 barrel... Of course you could do the 308, but even that is beginning to get kind of expensive to shoot these days on store bought ammo. I love the 308 personally, and plan on buying at least one, maybe two before the end of the year. Then again, I reload, so ammo is NOT an issue for me.