7mm and 30 diameter cartridges. You don't need magnums unless you want to. If you don't reload, find a great factory hunting round and you should be good. As for specific caliber.... Just pick one that you like and can handle the recoil.
Yes. 30-06 to 325 WSM, then 7mm-08, and now looking back at the 30-06 sitting in the safe. The 7mm-08 started as a cartridge for the wife, but after i started handloading it, I had to get a rifle in that caliber. But you can usually never go wrong with a rifle you have used for multiple years.
Not really. I tried 4 shops in three days. Most places will have budget complete setups that are great to start with. I tried a few that I thought I would love and they all felt different. Ended up with a Bowtech Assassin that I still shoot after 10 years. I shot it stock then upgraded the rest...
You have to try out and shoulder a few. Another consideration I have to take is that I don't like detachable magazines. So I end up going the Howa/Vanguard route quite a bit with rifles.
I live in NW South Dakota. Archery antelope is fun if you have the time and patience. Just remember that Archery Antelope is closed during Rifle Antelope. Usually beginning of Ocotober for 2 weeks then Archery resumes for a little bit, but then they are usually riled up.