Depends team to team and founder to founder. I've seen early stage startups where most ICs were able to self manage, but others where some form of structure was needed. At the stage that you mentioned, it's natural for founders to end up hiring an Engineering Lead.

> consider elevating a few engineers into informal tech leads

It is potentially risky - I've seen plenty of talented engineers flounder because they were thrust into an ill-suited management role too soon, but I think if someone is motivated and eased into the role they tend to be superior to an outside hire.