On 10074, with Start not working at all, I tried adding a new administrator account. After log in, Start randomly gave signs of life, a couple of times launching with a lag of several seconds. As a matter of fact, unusable. Reverted back to 10049, where Start is quite snappy. Might be a combination of upgrade from previous builds, permission issues, old/new account, UAC disabled, local account/MS account, hardware (specifically lack or RAM?). With UAC off, I used to access Settings via Control Panel > User Accounts > Make changes to my account in PC Settings. Thanks, T-S, for the shortcut.
Thanks for that tip T-S !! Works a charm, good to know. VERY useful, now I can install Classic Shell and just forget about non-working Start menu.