Yeah, I think the 2nd type of relationship is much worse than no relationship, I'd say the problem there wouldn't be with someone being vulnerable, it's the problem with the relationship...
Yeah, during school it's difficult since you are forced together with potentially toxic people. As an adult you can choose at least in personal life and to an extent workplace, although sometimes workplace can also be difficult to get right.
I'd 100% rather be alone than around people who might judge or use in someway against me anything about me. It would feel internally disgusting for me to think that someone might be trying to get at my expense and that I'm not around people who are there to try and build each other. What a waste of time.
The thing is, what you want is specifically a relationship where you are not vulnerable. If you're not worried about the consequences of the things you say, there's no actual vulnerability. You're just adapting to a safe situation. In which case good for you and you partner.
Ultimately, what I'm trying to do though, is to build myself such a life that if my internal principles are good, I shouldn't have to worry in most cases about what I'm saying since I want to believe in my principles. I want my interactions with people to be win-win, and I want to surround myself with people who want that too. If someone displays lose-win behavior, I should always naturally have the "moral" upper-hand assuming other people around me are reasonable. And if none of the people around me are reasonable, I should go and find the reasonable people.
People seem to be romanticizing the term "vulnerable" though. I think it would be important to go deeper into this. What does "vulnerability" exactly mean. I have had depression, anxiety diagnosed in the past and addictions and other similar issues, are these vulnerabilities because they may interfere with me acting optimally or are they vulnerabilities because they provide someone a tool to try and get at me if they so wanted because they think there's stigma around those labels to influence others to think worse of me?