To keep your SVGs as small as possible you want to remove anything unnecessary. The most well known and best (at least I think so) tool to post process SVGs is SVGO. This strips out all the code that isnt’t needed — but remember to be careful when using this if you plan to manipulate with CSS / JS as it will also strip out any layer names etc you have added. The best thing with SVGO is it can be added to your build process so it is automatic (or you can use a GUI to do it yourself).
