Hi,
YC is an commerce platform, which implies it is a complex large project with a lot of things to be considered. Not all functionality maps to every business processes so some customisation is always need for larger projects.
In previous response SEO and analytics was just some examples of things that cannot be achieved even through customisations. SEO is a very important part of e-commerce and not just because this allows you to index pages by search engines but also for bookmarking pages, or even cases where customer type a URL that they remember (yes, it happens a lot, we receive a lot of statistics from our clients, you will be surprised by the habits of common online shopper!).
So to answer your question about Angular, yes you can do it. We would recommend looking at the REST API web app module. In terms of customisations you will find YC to be quite flexible, so whatever extra functionality you need can be easily added on.
But you have to understand that there are so many different projects with so many different requirements that you answer does not have a simple yes/no answer.
Regards,
YC team