Can I limit User access to viewing only?

You can actually have an unlimited number of reports only users, if reports are good enough. (And if you are on Plus) Genrrally if a user can see an individual transaction they can also edit that transaction See this article for types of users. https://quickbooks.intuit.com/learn-support/en-us/set-up-users/user-types-in-quickbooks-online/00/186238