after first contacts?

Stick with those two. If you didn't get a first contact from other places it's not worth going at this point.

You should rush more lower houses. It's not a great idea to stay for more than an hour/hour fifteen at this point, so you should have at the very least a total of three hours to try more houses. First contacts are essentially meaningless; in most cases lower and top houses will give positive contacts to any and all rushes that won't turn off their targets. For that reason its best you use the about 3 hours you'll have to go around to more houses. Considering:

Top Houses: Not gonna take someone they met this late
Mid Houses: More likely than top houses to give a positive contact meeting a rush this late, but still most likely a waste of time
Lower: Will give a positive contact to rushes they meet this late if they like them

Don't waste your time with more top houses, or really mids. If you're serious about getting a bid, try going to smokers at one or two lower houses in the next two days

Large friend groups all get first contacts if one or more of your friends is a top recruit or someone all the bros like. But you are just getting strung along and will most likely get cut in the later rounds.

I'd say show up, show interest at all the houses. Not that you would be busy divinding you time between only two. Plus it is very "unattractive" when a guy spends aaaaaalll his time at this one place - brothers might get annoyed, you know what I mean? Its sort of like playing around with girls, you want to show that you have options. So add more lower tier or mid tier or fool around FIND SOMETHING YOU LIKE while attending all houses that gave you contacts. You have nothing to lose. Advice: when leaving a party at night after an hour or two politely say you're heading to another house, don't disappear without a word. Nobodys gonna get mad, rush is rush