It depends on who the embedded form is working. Quite a lot of them also include a link to CSS styles which may be overwriting your webflow styling: hence why things aren't matching up.
The easiest option i've found in these instances is to go into the embedded code itself and add additional classes to it.
So for example if you have an input field that looks like this:
Add an additional class to it as below
<input class="email mywebflowclass">
Then create a new class in Webflow with the name "mywebflowclass" and style is accordingly. This should then ensure that your styling is carried through to the live site.
PS. You'll need to use class names that are different from the existing names in the embed to ensure it pulls through the correct styling.