You are committing - not committing in the meantime. A WL means you have not been accepted.
So get your mind around - the one you choose is where you are headed and both are great!!
At Lehigh, you got your dream!! That says a lot. Out of state doesn’t matter - it’s a private, not public university.
Same with NEU - you got need based aid - but your state of residence plays no part in the #.
So you bring up an important part - a 5th year.
If you want to be a chemical engineer, it will be needed at Lehigh - and at what cost? It’s another year of school and a lost year of earnings. You should check with Lehigh to ensure aid will still apply.
If you don’t want to be an engineer, then you don’t need an ABET accredited engineering certificate - you’ll have the general engineering degree.
Given what you state, Northeastern provides a lower cost and quicker opportunity to be employed - as a chemical engineer or something adjacent as you noted (product manager).
But if you like the IBE program, it’s great but it will come at a cost - unless you leave after four years at which you likely won’t be able to become an engineer - but that might not be what you want anyway.
I guess what I’m saying is NU gives you, in my opinion, more flexibility and certainty.
Best of luck whatever you decide.