So, some questions: what era are we going to play in?
I already said 20s or 90s. Decide which among yourselves.
Does everyone have to know everyone else already or can we form groups of e.g. 2-3?
One group please. i don't want to have to construct multiple scenes, so please refrain from splitting the party, other than in downtime.
Do you need stats rolls at this point (and if so, do you have any advice / limits?)?
Go by whatever the book says, unless the book is being stupid, in which case you may have a bit of reasonable license without requiring case-by-case approval. "Whatever all of you agree" upon is probably a good enough litmus test for whether to regard the RAW as unreasonable on any particular point.
What location will the game take place in (e.g. rural or city? / What country?).
Probably mostly USA, but no particular part of it, with likely an overall globetrotting theme. Without getting into politics, I'm aware of a strong rift between city and country people in modern America, and I don't want to worsen it by doing the kind of "degenerate backwoods indbreeds" stereotyping that city-loving HPL often indulged in, nor by doing the polar opposite and portraying rural dwellers as saints untouched by the corruption of city life. Plan on the game making no real distinction between rural, urban, and suburban locations or lifestyles; any creepy atmosphere that is cultivated will be specific to particular locations, and will attempt to avoid trading on any specifics which overlap with modern bigotries.
Are there any other restrictions we should know about or do we have carte blanche?
Within reason. I'm uncomfortable with all this "let's play the cultists" talk; if you go that route, Sanity rules will be *strictly* enforced and your character will soon become unplayable (needing to either be retired to the asylum or being seized by me as a villain for the campaign, either way forcing you to make a new PC), while if you play a reasonably sane and normal person who dabbles in some of the safer spells, and takes proper measures to process whatever immoral or lunatic activities they may get involved in, I can probably go a little easy on you, let you do some stuff "for fun" as opposed to maintaining an extremely faithful Lovecraftian tone.