For Admin Panel you basicly need only datatables and form validation. For the first there is 5kb plain JavaScript library - https://bunnyjs.com/examples/datatable/
Second example about Validation I am going to finish on weekend.
There are actually already many simple packages in BunnyJS, I am just slowly writting docs when have free time, so if you will need any help or anything else, feel free to ask me directly.
Also jQuery with it plugins could be a good option and there are many lightweight plain JS components available on GitHub today.