Should your Meta descriptions be the same as your product descriptions?
Is it advisable to keep the product descriptions more detailed and the Meta descriptions shorter and more focused? Can overuse/repeating of keywords in meta descriptions negatively impact SEO performance?
Should meta descriptions across different product pages be similar/ share sentences or should each be completely unique to the respective page?
It’s fine for meta descriptions to be the same as product descriptions. You can make them whatever you want to be, without worrying about negative SEO implications for overusing keywords, etc. I’d just make something that is useful and compelling to the user. The meta description’s content is not used directly for ranking, but how well it appeals to real users and gets them to click on your results can improve rankings indirectly.
As long your snippets are relevant, whether they’re pulled from the meta description or page content, you’re probably fine.