Can you help me evaluate which SaaS idea I should build?

So I have three ideas in mind, but I'm not sure which one i should build and which ones are garbage. It would be great if you could give your opinion on them! Feel free to use these ideas as inspiration :)

Idea 1: Multi-platform financial KPI tracker

I have noticed that some businesses are juggling between multiple payment providers like Stripe, PayPal and so on. This could make tracking financial metrics a hustle as you have to pull data from each provider individually. The core idea is to build a platform that tracks these metrics for you in one place, as well as provide additional features.

There is already bigger competition, but they only focus on the KPI tracking aspect and less on the multi-platform part.

Target customer base would be medium to small businesses. Payment can be monthly.

Idea 2: Social media unfollower

There is this principle called "follow for follow" where you rapidly follow a large user base and hope that some of them follow you back in order to grow your account. When a user doesn't follow back you ideally want to unfollow them as a large following count doesn't look good when your follower count is small. Most social media networks like Instagram don't provide features to see which of your followers follow you back, so you have to check individually. A simple mobile app that provides this missing functionality for multiple social networks could prove useful.

There is already competition with around 5 mil. downloads, but their UI is outdated, and they only work with Instagram.

The target customer base would be regular users. Therefore, monetizing would happen through ads.

Idea 3: Connect content creators with sponsors

Small YouTubers struggle to find a video sponsoring. A platform to standardize the process of finding sponsors could help a lot. I would have to reach out to businesses as well as content creators and get them to use the service. Sponsors could create listings including payment information and the required reach of the content creator. Creators can apply to the listings and both share their contact information.

There is already bigger competition, but they focus on bigger content creators.

Target customer base would be regular people as well as businesses. Maybe only the businesses have to pay monthly to create listings.