I have never done anything but in-place upgrades on all my own machines that did not start out life as Windows 10 machines, and all worked perfectly.
I would always do an in-place upgrade, anyway, just to get the existing license converted to a Windows 10 license stored on Microsoft's servers. If the system works afterward, and barring an unstable existing installation or one that has underlying corruption, it should you've saved yourself a lot of time and effort.
If the system doesn't work well, then you can do a completely clean reinstall.
But whether one is doing an in-place upgrade or a completely clean reinstall, it is vital to have taken a full system image backup of the current Windows installation as well as a separate user data backup for all users on the machine. Far, far better to have these and not need them than to need them and not have them.