I have been running a Sunrace 13-28 7-speed on my Campy NR bike for about 5 years (wore one out and on second), but as
BFisher noted it shifts so smooth compared to any vintage freewheel and they are cheap.
On the exploratory end, I did add a Sunrace 11-36 10-speed freewheel to a Suntour VX long cage and the RD handles it quite well. Friction shift with Suntour bar end shifters makes gear changes tight, but this was my setup for commuting and details here in this thread. Weight is the tradeoff.
Vintage on Modern 11-36 Freewheel