hello, yes, the situation is changing dramatically since there are almost no html5 incompatible browsers and the new css3 gives lot's of ways to approach this (as far as nobody is using IE browser any longer and Edge gets updated automatically). also Safari on Apple products is not html5 compliant and thus can cause quite lot's of troubles.
the main question is how should they look like ?
this seems to be a standardized way for html5 browsers:
https://www.w3schools.com/howto/howto_c ... eckbox.aspit's using new CSS selectors and keywords and thus it should not break compatibility with old browsers. (they would just show the radios/checkboxes normally)
the old approach was to hide the real radio/checkbox with position outside viewable scope and render an image (or else) at the place of the radio.
the new approach uses vector fonts (such as font awesome) or SVG's directory to render radios/checkboxes.
note that select dropdowns are still quite tricky to get them formatted same on all platformas.
the example link above expects the radio/checkbox to be inside label wrapper which may not be always possible or ideal.
the problem with formatting these in OPC is that we try to make OPC themes compatible with most of the Joomla/VM templates available and thus if we style this too much, then it may not look consitent with your own template. the answer to this could be a css-less theme like the one we included as "ja_brickstore" which doesn't use our CSS and uses either VM's original CSS or template's overrided CSS.
let me know how could i help you further with this.
best regards, stan