Notes app very slow on iPhone 7

I've been using the Notes app for years to take notes with screenshots. I now have around 2,000 folders in the app. The storage is now 100 GB and on iCloud. Thus, every time I open the app, two of the following happen. It either:

1. Takes 5-10 seconds to load, then I can use it as normal or;
2. Freezes for 5-10 seconds, crashes, then it works as normal when I open it again.

It wouldn't be much of an issue if I didn't have to use the app almost everyday and need to open and close it regularly. This is because I would watch an educational video on Youtube, take a screenshot of it, open the Notes app, then paste the screenshot and type in notes, then open Youtube again and repeat the process. As a result, the frequent opening of the Notes app causes the 5-10 delay to add up quite a bit.

I have 2 questions:

1. If already hosted on the iCloud, how come the used space is still located on my iPhone storage? Shouldn't the purpose of the iCloud to alleviate the space?
2. If I buy a new phone such as iPhone 15 or 16 with 1TB storage, would this problem still persist? I presume with a much larger storage capacity and faster processing, there should be no more delays?

Thank you!