We have 16 store views inside magento2. I want to know is there any performance issue with lot of stores? Our website is slow on product page and checkout page.
The short answer is yes you will have performance issues.
Magento 2 scales a lot better than magento 1 but 2.3.2 will have issues with dealing with pricing on templates as part of loading products via collections and also you will have issues with crons taking a while to run.
You can profile code to work out if extensions are impacting your load time. But just add 10 items to your basket and go to checkout to see if you are happy with load times.
There are various caching mechanisms which can be used but a cache should be used to support the speed of the site. It should not be solely responsible for keeping the site alive. Look into cloudflare. Distribution plus protects site from traffic generating bots. Plus additional features such as CDN.
The exact spec will depend on the number of concurrent visitors but you will no doubt need a dedicated box. Perhaps ignore cloud or virtual host type solutions for now. You should aim at at least 4 cores minimum.
Obviously try and use all the latest and greatest components in your stack. Nginx, php7.2 plus, redis if it is a high traffic site - not if it's not. Look into search providers like algolia. Again takes processing away from site.
Look into new relic and blackfire for snapshots of before and after technology or code changes. This will give you an idea on whether the changes are making a positive impact.
But with the right planning and investment in the right areas you can manage the performance of the site and make the extremely flexible magento framework work for you.