Q: Shared albums?

1. can a shared album be shared with anyone even without a Mac or iOS device?

People without a mac or iOS device can browse a Shared Album on the web, if you publish the shared album as a web page and send them the link.

See this link:  iCloud: iCloud Photo Sharing FAQ

2. Will my shared photos always just show up on other peoples iOS devices when I add them to the shared folder?

When you add a photo to a shared album or add a comment, the photo or comment will download on all devices that are signed up for the Shared album. The recipient will see an alert, depending on the setting for alerts - typically a notification in Notification Centre or a number badge on the Photos icon (iPhoto icon, Aperture icon).  On a Mac the recipient will have to have Photos, iPhoto, or Aperture installed to be able to browse Shared albums.

1. I can make multiple shared albums in Photos and with each album choose which albums are shared with which people and they do not need to do anything other than clicking on the shared album on their iPhones or iPads and they can see all of my shared photos?

Your friends have to accept the invitation in their email notifications, and then the shared albums will appear in their system photo libraries on the Macs or on their devices, or they click the link to the web page, if you publish the album.

2. Can I easily remove access to the shared albums to everyone or certain individuals?

 

yes.

you can either delete the shared album or remove individual subscribers.

Photo Stream and iCloud Photo Sharing limits

The list Eric Root posted is showing all limits.

1. You can create up to 100 shared albums.
2. The "5000" limit applies to each album separately.