sororitys

Phi sig is the only sorority with an official house. Every sorority has houses though. For example, AEPhi has the infamous "42", DZ and DPhiE have houses, and I'm assuming AXiD does too but I'm not sure about them honestly.
Phi sig for as long as I've known them doesn't really throw parties in their official house. Most sorority girls go to the frats to party. Maybe at other sister's houses, but generally when a sorority has a house there are many rules given to them by nationals they must follow.
This isn't to say phi sigs don't party, all the sorority girls party. I definitely wouldn't put them in the top three party sorority list though. That would go to the #mostfun AEPhi, and then a tie between AXiD and DZ with DPhiE very very close behind.
Having a house doesn't make a sorority any more or less close. It really is about how the girls treat eachother, and what they do together that determines that. Every girl from these sororitys will bend over backwards telling you her sorority is the closest, when in reality they are all pretty much the same.

Lastly, you do not need do join Greek life even if you do recruitment! You can drop out of recruitment at any time you feel it is not for you, you can go through all the way and decline your bid day card, you can accept your bid day card but then drop that sorority (but cannot rush again for a year), and should you be initiated you can disaffiliate from the sorority (but this tends to get a little awkward).

Hope this helps you!