You don't do shit about differentiation. You are intrinsically differentiated (from the 20somethings you seem to be worried about). Tell me what it was like in the 90s.
You've got the experience. Just amaze me. Internalize that its conceptually impossible to be worse than the 22 year old kid. Show me that you make an effort to keep up with the times, and then tell me about the old times.
^ That may not work with the hipster founders who just want to be hip, drink beer while "working" 60 hour weeks having raised 15M from a16z (for a16z, 15M is a throwaway round. their funds are too big for that kind of bet to make sense.)
You won't get into brogrammer companies. You wont fit in. Theyre right in claiming that you wouldnt be a culture fit. But is that something you aspire to, anyway? People like you can replace 20 of those clowns. I'd rather pay 220k for one real engineer than 120k each for an army of bumbling idiots. Any day.
But you've got to bring the skills.
Don't sell yourself-- nobody wants a supplicant. Convey your Senior status. Focus your conversation on him. What are his priorities? Where are they struggling? Has he put thought into what sort of culture they're trying to build? What does success look like?
You will standout by asking good questions, demonstrating you have a deep understanding of the space. Mindset is important - you're here to determine if this is a good match. He needs to sell you.
Seriously besides that basically as stray said, treat them with respect and realize they are quite smart or they wouldn't be where they are. Be willing to learn from whomever stands with you or in front of you regardless of age or status and you will never go wrong.
Also from experience, don't avoid the topic bring it up and make it a non-issue for them. Legally in an interview they can't ask direct questions as they probably want to. Do it for them to take the pressure off, that helps a lot. If you aren't hung up on it they won't have any reason to be either.
Just treat them like adults and answer their questions.
You'll be fine.