I don't have a direct answer, but I do have some additional thoughts/strategies...
1 - People are different
I have worked with folks that would be stressed out no matter what the situation. I know others who are almost disturbingly cool under extremely stressful situations. Bottom line - stress level vs. reasons for stress are highly personal.
So - most important - where does YOUR stress come from? For some, it's the perception of others (wanting others to see you as good at your job, likeable, etc.). For others it's the demands between work life balance. For others it's actually being able to complete objectives.
That's the biggest element of "would this job stress you out"?
2 - Can you redefine the mission?
Hard to know until you get into it fully, but it's worth it to have a talk with the boss about what your powers are and whether you can eliminate some elements of the stressors. For example:
if the fires and emergencies come from buggy code, and poor quality control, can you change how you do testing if you are the lead? Can you have time to build additional regressive tests, or improve the test environment to give you better feedback? Can you change the peer review process or get better design practices?
if there are issues around conflicting and changing #1 priorities - can you set up a communication structure that makes it clear what priority will and won't be staffed when priorities change? Can you create a mode where when you accept/respond to a change in priority you have the ability to point out what won't get done as a result? I've seen new leaders get hung by this a lot - that they forget/don't realize how important it is to both accept a change in priority and react urgently but ALSO to make it clear what you won't do.
can you and your boss work out a reasonable definition of what good work on your part looks like? Something that is actually achievable in a normal # of hours?
can you staff a coverage model, so that if you have to support customer escalations off hours, it's not always you, but it can shared in some schedule able way across a team?
If your boss isn't open to talking about how you might change the way you, as the lead, get the work done - then I would doubt he's giving you enough autonomy to take the job and make something good out of it, and he just expects to overwork you and not really change anything.
If he's supportive, but says "well, that's not really controllable" - then it still may be a red flag, since there are some jobs that just can't be fixed.
3 - Overtime - controllable - yes or no?
Specifically on the topic of overtime, as a manager, I'll say that I'd be cagey too. If someone on my team came to me and wanted a 100% guarantee that they'd never have to work overtime, I would counsel them to find another team. IMO - there's an element of knowledge work where you make your own overtime.
What I usually can promise as the boss, is that I'll do my best to make sure the team is giving me reasonable estimates, and that I can support a work/life balance when we take on emergencies that are needed to support the business. But if the need for overtime is coming from a way-too-short estimate, or I'm asking someone to work late because the business has a crisis with a deadline --- then as the boss, that's not something I can easily prevent. But at least some of that (too short estimates) - is under the individual's control, because I'm relying on the team to give me the estimates.
That's a nuanced conversation that not every boss is capable of having. And when an employee is stuck in the idea of "no overtime, I mean it, never, never, never" - then you two may be at an impasse.
But I've gotten a lot of good outcomes from getting super clear about what an "emergency" is, and how having emergencies WILL slow down the day to day planned work, and it's possible to work in a place that accepts that emergencies at a higher-than-expected level will interrupt planned work. It's also reasonable for the boss to expect the team lead to consider a normal level of emergencies when planning work.
4 - Stress & Leadership
My experience has been that team leadership is a different level of work, and one that can be difficult to put down. Even if you aren't being demanded to do overtime - the dynamics of leading people and getting a plan to come together and conflicting priorities managed is real work, different work, and a learning curve that can be either "stressful" or "energizing" - depending on how much you enjoy it.
For me - at least - it's harder to put the leadership stuff down at the end of the day. Code/design is much easier to shelve for tomorrow. It's no so much being trapped at a key board, but the fact that your mind will stick on issues of the day, regardless of when you go home.
I think that's a healthy kind of growing stress... that comes from being interested and learning new things. But it IS a kind of stress, and one that I would see as hard to avoid in this particular type of job change.