Can I integrate third party tools to my CRM?
You can integrate virtually any tool you want with code snippets. They are available on the Premium plan, and they allow you to use JS code.
Another option is to use Google Sheets as a middleware, receiving data from third-party apps, and serving it to Softr. Google Sheets is particularly useful since it allows you to use Apps Script, adding all the possibilities of coding to no-code projects.
How to use Softr to send emails to users?
You can use the Airtable email automation to send one-on-one emails to your users. You could use a newsletter system with webhooks to automatically generate newsletters from your CRM
What is the cost of using Softr to build an Investors Relations CRM?
You can build your investor relations CRM for free. You can make it better with the premium plan, and you can use other premium tools if you want (such as Zapier).