Yes, you can use UltimateWB with all of these, although how you use each one depends on what you're trying to do with it.

Google Forms: You can embed a Google Form directly into an UltimateWB page using the embed code from Google.

But you may not even need Google Forms. UltimateWB has a built-in Forms & Surveys Builder, so you can create forms and surveys directly in your website without needing a separate form service or WordPress plugin. You can create your own fields, set up submission options and email notifications, and integrate the forms into your pages.

Here's the User Manual topic with more details:
How To Create And Integrate Forms & Surveys In Your Website

BlueSnap: If you're looking to use BlueSnap for payments, you don't have to use WordPress just because BlueSnap has a WordPress integration. BlueSnap also has other integration options. If you tell us what you need BlueSnap to do on the site, we can let you know what would be involved with UltimateWB.

Blackbaud: This one depends on which Blackbaud product you're using and what you want to do with it. Blackbaud has several different products and services. If you're using something that provides an embed, API, or another way to integrate it into a website, that can generally be incorporated into an UltimateWB site as well.

And if you're specifically interested in WordPress, you don't have to choose between UltimateWB and WordPress.

UltimateWB has a built-in WordPress blog option, so you can use WordPress for your blog while using UltimateWB for the rest of your website. You can also install WordPress plugins on the WordPress portion if you need a particular plugin.

One thing to point out, though: you don't need to install the usual WordPress SEO plugins just to get SEO functionality for the UltimateWB WordPress blog. The UltimateWB WordPress integration is optimized and includes SEO functionality, so you don't have to start adding the usual collection of WordPress plugins just to handle basic SEO.

So if your main concern is that these services require WordPress, I wouldn't consider that a reason by itself to choose WordPress. UltimateWB can handle a lot of this directly, and you can still use WordPress where you actually want it.

If you tell us which Blackbaud product you're using and what you need Blackbaud and BlueSnap to do, we can give you a more specific answer.