You only need the mariadb client for a computer that will work with a database on a different computer. If you have only one computer then mariadb alone is enough. If I remember correctly you don't need the client for a computer using the PHP native mysql client extension even if it isn't on the same computer as the server, but I've never tested that.
I only build mariadb so that the extensions I maintain can be compiled with support for it. I only use it enough to build test databases so "make check" can verify the extensions work like they should. I used mariadb for a month or two, but I was an Oracle DBA for many years and I soon realized mariadb was to databases what windows is to operating systems. I switched to Postgresql and things just started working like they should, like when I switched to Linux (in the mid '90s).
I'm sorry, but I'm at the limit of what I know about mariadb. Every time this comes up I ask that someone who actually cares about it take over maintaining it, but you can see that hasn't happened yet so this is as good as it gets for now.
I maintain the PHP, Apache, and Nginx extensions also, and I test them against mariadb, Postgresql, MS SQL Server, and Oracle on both 32 and 64 bit.