On the subject of overnighters of girls you know vs new girls my experience is that overnights with unknown girls were always better , less awkward , less expectations , everything was fresher and more fun , and better sex and generally better.
I think you would have to really get on well with and be totally comfortable with an SP to step up to an overnighter and for it to work. When ive overnighted girls that i knew i often found it a slightly awkward progression , plus i kindof sensed the elephant in the room was the whole question "why has this guy gone from fucking me for an hour to now an overnighter , is he soft on me or what ?" it shines a light on the fact that you might like the girl , which in the context that shes a WG might be a bit cringy and a bit uncomfortable. If shes a new girl then there wont be this psycological baggage , it will all be fresh and a clean slate and you can just ride the wave and fuck her.
I overnighted with one girl i knew and it was so awkward we never had any physical contact at all , it was like so now we are kindof freinds i felt i had to respect her boundaries and stuff. Obviously different people will adapt to different situations differently and others will likely adapt to the overnighter with a rugular girl better than me , but personally i have no interest in having a hooker over and feeling i have to host and entertain her , id rather have a whore over fuck her when i want and otherwise let her entertain herself watching tv or something.
Its worth trying just for a different experience but id question the motivation for doing it as logically in a sex transaction from a sex:cost perspective it just isnt good value for money.