If my device is 64 gb so can i see all my 200 gb icloud photos in my photos app?

You may be able to if they are optimized:

How to check the storage on your iPhone, iPad, and iPod touch - https://support.apple.com/HT201656 - "If your device is low on storage, iOS automatically optimizes its available space while installing an app, updating iOS, downloading music, recording videos, and more. To make more storage available, iOS can remove some of your items, like streamed music and videos, files in iCloud Drive, and parts of apps that aren't needed. It also removes temporary files and clears the cache on your device. iOS only removes items that can be downloaded again or that aren't needed anymore."

Keep your photos safely stored and up to date on all of your devices - https://support.apple.com/HT201313

Set up and use iCloud Photos - https://support.apple.com/HT204264

--> Save space on your device

iCloud Photos keeps all your photos and videos in their original, high-resolution version. You can save space on your device when you turn on Optimize Storage.

Use iCloud Photos to store photos in iCloud

https://support.apple.com/guide/photos/from-icloud-photos-phtf5e48489c/mac