Hello there and welcome to the Wowza support forum. Sorry for the delay on getting back to you on this.
I will do my best to answer the questions I can, but I would also suggest you contact the sales department for further information.
First, Wowza does not have a hard limit to the number of connections it can handle, a single instance of Java is capable of saturating up to 5Gbps of bandwidth. So this would be a limitation as to how many concurrent connections you can have which will vary based on the bitrate of the streams being viewed.
Second, there is no limit (that I know of) for streams coming into a single application. So users can have multiple camera feeds coming into the same application.
For playback, you can use JW Player as a cross-platform solution, supporting many standard clients: