The documentation you pointing to is the documentation for the v0.20.0 of web3.
The v1.0.26.beta is available now, which documentation is also available here
beetween v0.20.0 and v1.0.beta many changes happened. One important is the implementation of the web3.eth.accounts part.
on v0.20 web3.eth.accounts retrieved only an array of the available accounts.
on v1.0.beta, the web3.eth.accounts retrieves a list of functions as described in the doc.
However as this version is a beta, many functions can be still missing, and many can be buggy.
There's no real limitations others than the one that are already described in the doc. However, you'll probably find some bugs using those libraries. If that happens feel free to open an issue on the project repo on Github.
Last point regarding the Web3 library : it's no specificaly intended to be used on client side or server side. You can use it for both. However if you want to make a complete decentralized app you'll need to use it strictly on the client side.