Re: What model 700 to grow into?
There really isn't that much to a Rem700. Receiver, barrel, stock. How much modification are you talking about? Rebarrel- may also need a new stock depending on initial and new barrel contour. New stock? May not be able to find a stock you like that will fit your barrel contour. I guess the real question is, short, long, or magnum action? So, what cartridge family are you thinking about? A 308win is plenty effective out to 800 and many stretch them out to 1000. A 300win mag will reach out a bit further. Given that as you "grow into your rifle" you are likely to rebarrel and restock- keeping only the action- I would suggest "inexpensive." Many people buy an inexpensive "donor rifle" knowing that all they want is the receiver. I think that most here will need more information in order to answer your questions.
Glass is as important as- if not more so than- your rifle. You cannot hit what you cannot see. Expect to pay as much for your scope as you do for your rifle. Nightforce scopes are well regarded for performance/cost but there are definitely higher end options- much lower end as well. While the law of diminishing marginal utility does apply, by and large you get what you pay for.
Provide some more information and I am sure that the more knowledgeable members will chime in with good recommendations and suggestions.