The second bit IMO is wrong (OLG).

And the first bit is the wrong question to ask.

It is better to ask instead: "How should we organise public finance so we do not need to answer that question?"

E.g. NGDP perpetuities. https://twitter.com/TheStalwart/status/1353032870999314432

The whole point of market economies is to let markets answer questions that economists don't have useful answers to.
Like: "How many apples should we produce?"

Ultimately, the bond market must answer the question "How much debt is too much debt?"

BUT:

What happens if the bond market changes its answer?

And that's where something like NGDP-linked perpetuities kicks in.

Bond market won't let the govt roll over the debt?
So what. The govt doesn't need to roll over perpetuities.

NGDP growth comes in lower than expected?
Too bad. The bond market takes the losses.

The analogy isn't perfect (so don't push it too far), but:

A govt issuing NGDP perpetuities is like a corporation issuing shares.
No debt worries.

And the whole "Too much debt?" question hinges around the "r<g vs r>g?" question.

And NGDP perpetuities give a very fun answer to that second question. (Hint: solve for the PV of the infinite coupon stream if r<g)