So yellow/red flags:

1. ARR in the XX mil, but you are taking a pay cut?

2. You will declutter the tech stack and work on exciting products?. Usually in a startup (or any other company) - you touched it, you own it. So once you declutter the tech stack, I am not sure that you will have time to work on the other exciting projects (or even if they will still be relevant).

3. Why do you even need to declutter the tech stack? what happen to the original programmers? what happen to proper process? do they have unit tests? CI/CD? Can you sandbox this code in a micro service and just call it?

4. The option thing looks like they are increasing your switching cost. I.e. once you buy the options than you will be limited in your moves both inside and outside the company.