Well there has been changes yes:
Parts scaled up.
Nova - modified parts + struts strength.
How parts collide with each other differently.
Importantly Engines now have Atmo/Vacumn power profiles, which is true to real rockets.
I believe these have affected power/weight ratio's
Also ASAS struggles to control the new larger parts in space.
As a tester, generally we tested for bugs, now how sutle changes affected rocket performance.
Remember his is a Hybrid update. Version 17 should add further parts plus fully balance them.
Look on the bright side, another reason to relearn your rocket creation skills an bounce some kerbals off high atmo or off each other.
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