How to use Mail Cow in my setup?

I intend to send (a) emails for marketing campaigns and (b) emails for normal correspondence eg. Talking to customers.

For (a), I intend to run an email marketing application like Sendy / Mailwizz on a Digital Ocean droplet that is connected to Amazon SES.

For (b), I intend to install Mail Cow on a Digital Ocean droplet.

Question 1: Do I need two separate Digital Ocean servers for (a) and (b) or can they be the same?

Question 2: If they can be the same, is it recommended they be the same?

Thanks.