[Pov]

For the specific questions you ask the answer will be card room specific. However, as a general rule the "modern" NL game has a fixed or at least maximum buy-in unlike in limit so just ask the brush (quietly) when you get on the list. Where to buy your chips is pretty much dependent upon what the room prefers regardless of limit or no limit. I suspect there is a higher chance they will want you to buy-in at the table in no limit so they can enforce the buy-in size restrictions more easily.