First off - it's .243 Win (as in Winchester) - that's who came up with this particular cartridge (in response to Rem's 6mm) .... by all accounts, same same. .243 Win is a necked down .308 ....
I think Win did their first rifles with a bit faster twist to better stabilize the heavier (deer-sized) bullets.
.243's one of my favorite "all-'round" calibers. For any varmit, to deer/antelope-sized critters, it's one of the best, IMNSHO.
Pounds (if you can call it that) a bit more than does the .22s tho' for extended bench/varmit shooting.
Ballistic coefficients are better than in the .22s so bucks the wind better while retaining much better down-range energies.
Assuming an accuracte & suitable bullet/rifle combination, lethal shots on deer/antelope is not too unheard of at 350+. For varmits, all you have to do is get the bullet there. A heavy bbl'd model may be not the best to be carting around in the field for hunting - heavy. YMMV
Scopes depend on what you'll be using it for.
For the long range shooting, a high power mag scope is obviously better than a lower power, but again, depending on if you'll be hauling it around or shooting from a "station," ....
An "always good power" is the 3X9 - a pretty good compromise - 3X for close-in & quicker sight acquisition & 9X for longer range. If you'll be doing strictly the varmit target type shooting, I'd go for a much higher mag - perhaps a 6X24 (or so).
Need some more info so we can all tell you what to buy.