In terms of privacy, you are giving your identity provider insight to each of the third party services that you use. It may seem that there isn’t too much of a difference between using Google’s SSO vs using your Gmail address to register your third party account. However, one big distinction is that Google would be able to see often and when you use each of your third party services.
Also, it may be impossible to restrict the sharing of certain information from your identity provider with the third party service. For example, maybe you don’t want to share a picture of yourself with a service, but that service uses user profile pictures or avatars. That service may ask (and require) that you give it access to your Google account’s profile picture in order to authenticate using Google’s SSO. You may be able to overwrite that picture, but you also may not be able to revoke the service’s ability to retrieve it. If you used a “regular” local account, that Google profile picture would never be shared with the third party service if you did not upload it directly. The same is true for other information like email, first/last/full name, birthday, etc.
There are other security and operational concerns with using SSO options. With the variety of password managers available, introduction of passkeys, and increased adoption of multi-factor authentication, many of the security benefits associated with SSO aren’t as prevalent as they were 10 years ago. The biggest benefit is likely the convenience that SSO still brings compared to other authentication methods.
Ultimately it’s up to you to determine if these concerns are worth the benefits of using SSO (or the third party service provider at all if they require SSO). I have a feeling the common advise will be to avoid SSO unless its an identity provider that you trust (or even better - one that you host yourself) - especially if you’re using unique emails/usernames along with strong and unique passwords with multi-factor authentication and/or passkeys.
I recommend that you think hard and properly access your threat profile. You are likely going to have to pay with either your wallet (eg: some sort of company incorporation, lawyer fees, forwarding services, and other privacy protection services), your time (eg: using “inconvenient” services, managing separate accounts, etc.), or both. It can be draining (in more than one way) and take away some of the joy that you’re intending this to bring you if you do too much to protect yourself. On the other hand, if you do too little then you can overexpose yourself leading to pricey or dangerous situations.
At a minimum, I would recommend incorpating and making sure your name is not publicly tied to the company in any way. You will likely need a person/company/lawyer to be publicly listed as an agent of some sort for the company. You should be able to have someone do this for you for a small-medium sized fee. Once you have that, do everything in the company’s name and ideally with separate phone numbers, email addresses, online accounts, bank accounts, and physical addresses as anything tied directly to you.
Some of that is to protect yourself financially and legally, but there are some obvious privacy benefits as well. Anything beyond that should be dictated by your threat profile.
As always though, follow best practices when it comes to security! Use strong passwords and use multi-factor authentication when possible (or ideally, use passkeys). Don’t reuse passwords (and ideally, don’t reuse email addresses for multiple accounts). Avoid clicking links in messages when possible. Don’t open suspicious documents (especially if they are unexpected). Verify the authenticity of any new person/business you interact with (especially if they contact you first). Be vigilant of all forms of phishing attacks.
Another piece of advice (that you didn’t ask for, sorry!) - if the process of making art is the thing that brings you joy and the materials are not too expenses, then just focus on making the art without selling it (at least for a while). At worst, you will realize that maybe this isn’t as enjoyable as you thought it would be with the added benefit of not needing to deal with all the troubles of working through all the legal/financial/privacy protections. At best, if you decide to get serious about selling it then you’ll have a larger product inventory and better understanding of what you like making most. It may also help you understand what you should price everything at (assuming you’ve made some of the items in larger quantities).