How much SEO is affect when changing domain

I run an email forwarding service call https://hanami.run and apparently it name is conflicted with hanamirb.org and we got a reasonable request to change our domains. I plan to conform to their requests and I would like to change our domain.

We launch in January this year and currently rank good on a few key words (we are able to be on frontpage of duckduckgo search for that query).

I did research and think my plan is to Setup 301 redirection from old domain to my new domain

I have a few questions:

1. How much this effect SEO?
2. Will my new domains take the rank of old domains? is there any way I can speed up this process?
3. How fast google will detect those changes?
4. Anything else I have to take care of to make this a smooth transition in term of SEO