Do the shows usually happen over the lake (Winnebago)?  Would hanging out at High Cliff state park be a good place to watch?

You may see some flights over there bu the shows are targeted for the main runway.

I don't think you are going to see much of anything aircraft-wise from High Cliff. The airshows happen over the airfield/southern end of the city and seaplanes are also docked south of the city.

Enjoy the park for what it is though. Its a fun place to hike around.

If you've never been there it's worth the ticket. So many cool old warbirds.
The airshow is over the runway.

Poor place to watch unless you have a monster telescope to see Oshkosh from 25 miles away.  Park at the Whitmann Field Terminal on the north edge of the airport.  Or a side street if the lot is full, and bring some lawn chairs up to the fence.

We used to camp on the grounds - Pauls Park - for 20+ years for the whole show, but when Paul left and the thing became all about money, we quit going.  I was flying and working on a plane back then, so my interest was was quite a bit bit heightened.  War birds are the big draw now whereas it used to be primarily about homebuilts and was a lot more family oriented.  Now it's all about big buck planes you could never afford.  That said, if you haven't been, there's a lot to see in a day or 2.  When we were there, I'd watch the first air show, then use that time to hit showers when everyone was at the show.  Some people now go just for the concerts.

Thanks for the info. Just wanted to know if I could see the cool stuff from the north side of lake while avoiding crowds.
Did see a semi formation of Piper Cubs today.

Use google maps and find side roads east of the runway. Park on the side of the road and enjoy