you can use the browser css tools to see the css styles applied. the font is inherited, the size and weight by the .btn class
to manually override at the element level with style commends, it need to be on the element, the anchor in your case.
normally you would use SASS variables to build the defaults you want, rather than override. or make more selective css classes
.btn.mybtn {
font-family: 'Just Another Hand';
font-size: 1.75rem;
font-weight: 700;
}
then:
<a type="button" class="btn mybtn d-block border mb-3"
asp-controller="Home"
asp-action="Categories" asp-route-category=@category>
@category
</a>