Hi,
reCaptcha by BestWebSoft is compatible with forms that are indicated on the plugin page.
To add reCaptcha field to custom form, please follow the instruction: https://support.bestwebsoft.com/hc/en-us/articles/202352499
If you have programming skills, then you will cope with this modification easily or we can help you, but this is paid service. As a rule, it costs $60, but the price can vary depending on the amount of the necessary changes and their complexity.
If you agree, could you please provide us with all the necessary details, and if you can, send the screenshots with the examples of the necessary reCAPTCHA field displaying and its future location in order we could more efficiently estimate all the customization work and its cost.