A project team has the right to expect the Project Manager to lead them. Leadership does not always mean hand holding, and it does not always mean full delegating. It means that you care about what is happening, you provide guidance and vision, you support, coach, train your team.
You look for opportunities to advance your team members, or your project, or your customer toward what they value. You freely share your knowledge, wisdom and skills in pursuit of the objective. You inspire others to do the same.
Your loyalty should be with your Charter; this is your objective. Your strategy is to deliver your project outputs on time and on budget. Your greatest tactic to do this is to lead, inspire, engage and guide.
Leadership should (IMHO) be biased toward recognition and reward, and away from punishment. We can punish people into obedience, threaten them into compliance – but we must lead them into true performance. Since this is best for your project – it should be your “go to” position.
Not sure what leadership is? There are hundreds, thousands of resources on how to be a leader. Go find them, read them, apply them. Be sincere and honest. The rewards are fantastically greater then the effort you will put in.
A project is unique. What it creates has never created before. You need some kind of definition of what it will be, how much you want to spend, and when you want it done.
You need a Charter.
OK, you might call it a project authorization sheet, or Budget Approval document, or any number of different names depending on your organization. What it HAS to do is authorize you (or a team) to start detailed planning. I must give formal permission to start using resources.
It HAS to give a high level description of the ultimate goals, the thing being created. It HAS to limit Scope. It HAS to define (in broad terms) what is is you are after. You could probably manage to do without early budgets, early timelines, early Risk Analysis. You can get these done during planning (although it is best to give some thought to this before you start). You might even get away without a business case, and trust to planning to reveal the feasibility of the project. Not best practice, but it might work.
But you HAVE to have a signed Charter that defines what you are after, and formally empowers you and your team to pursue it. (Notice all the absolutes here. HAVE to. HAS to. MUST. No kidding around.)
You, as a Project Manager, must insist on this foundation document, signed by the bosses. If your company refuses to use a Charter, or refuses to sign a charter, or refuses to allow you to create some kind of controlling and empowering document, start looking for your next job. They don’t deserve you, and they probably won’t be around long anyway.