Just wondering if there are any trade-offs to consider if I were to use Google Workspace (G Suite) instead of a provider like ProtonMail.
Using a custom domain with Google's paid service seems like the least drastic change and you get to keep using all their services. Maybe the support won't be as good, but the products and integrations are probably better than any other provider.
And as long as you do regular backups of your Google data, I think this seems like a good solution.
I had a commercial GSuite for an organization I was running. A Google bug wiped my domain and all my data. Support was automated systems all the way down.
I think the downside of Google is this happens about 100x as often as other organizations.
Google security also cares about Google's security, not your security. Your odds of account compromise go way up dealing with Google.
Using a custom domain with Google's paid service seems like the least drastic change and you get to keep using all their services. Maybe the support won't be as good, but the products and integrations are probably better than any other provider.
And as long as you do regular backups of your Google data, I think this seems like a good solution.