I'd like to know if I need two separate Windows 10 licences if I want to use one PC but with two different A/D accounts. The background is that my company wants to give every employee one account with and one account without admin rights.
Usually, Windows 10 license follows 'one license per machine' policy. Hence, IMO, you only need one license for the PC. Number of accounts is independent of license unless your accounts have a Windows 10 subscription.